Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Narrative) (Details)

v3.20.4
Long-Term Debt (Narrative) (Details)
8 Months Ended 12 Months Ended
Feb. 25, 2021
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Sep. 14, 2020
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Dec. 20, 2019
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Mar. 19, 2019
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Oct. 31, 2018
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May 15, 2018
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Dec. 20, 2017
Jul. 03, 2017
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Apr. 15, 2015
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Nov. 13, 2013
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Sep. 14, 2020
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Dec. 31, 2020
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shares
Dec. 31, 2019
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Dec. 31, 2018
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May 15, 2025
Dec. 19, 2022
Sep. 13, 2020
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Dec. 31, 2017
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Dec. 11, 2012
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Sep. 24, 2009
USD ($)
Debt Instrument [Line Items]                                        
Debt extinguishment (gains) losses, net                       $ (1,348,000) $ 2,244,000 $ 11,626,000            
Payments on long-term debt                       71,786,000 169,625,000 225,541,000            
Long-term debt acquired in business acquisition                       9,900,000 0 0            
Letters of credit outstanding amount                       $ 1,100,000                
Guarantee fee income, interest rate earned on outstanding guarantees                       0.50%                
Securities repurchased plan, remaining authorized repurchase amount                       $ 102,200,000                
SEACOR Marine Holdings Inc.                                        
Debt Instrument [Line Items]                                        
Guarantor obligations, maximum exposure, undiscounted                       7,000,000.0                
Guarantee fee income                       $ 100,000 200,000 300,000            
3.0% Convertible Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       3.00%                
3.25% Convertible Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       3.25%                
Convertible Debt | 3.0% Convertible Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage   3.00%                 3.00%                  
Aggregate principal amount                   $ 230,000,000.0                    
Individual bond, face value                   $ 1,000                    
Debt instrument, convertible, conversion ratio             0.0125892                          
Debt instrument, redemption price, percentage   100.00%                                    
Debt instrument, interest rate, effective percentage                   7.40%                    
Debt conversion, original debt, amount           $ 117,800,000                            
Debt instrument, repurchased amount   $ 34,500,000                 $ 34,500,000   57,200,000 4,900,000     $ 15,600,000      
Repayments of long-term debt and payments for conversion option in convertible debt                     15,400,000   56,200,000 4,700,000            
Debt extinguishment (gains) losses, net                     $ 600,000   (2,100,000) (5,400,000)            
Convertible Debt | 3.0% Convertible Senior Notes | Debt Instrument, Redemption, Period One                                        
Debt Instrument [Line Items]                                        
Debt instrument, redemption price, percentage                   100.00%                    
Convertible Debt | 2.5% Convertible Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       2.50%                
Aggregate principal amount                                     $ 350,000,000.0  
Bond trading price triggering contingent interest                       $ 1,200                
Individual bond, face value                       $ 1,000                
Debt instrument, contingent interest rate                       0.25%                
Debt instrument, convertible, conversion ratio             0.0190381                          
Debt instrument, convertible, number of equity instruments (in shares) | shares                       982,080                
Debt instrument, interest rate, effective percentage                       2.50%                
Debt instrument, repurchased amount                       $ 12,900,000                
Repayments of long-term debt and payments for conversion option in convertible debt                       10,900,000                
Debt extinguishment (gains) losses, net                       $ (1,900,000)                
Convertible Debt | 2.5% Convertible Senior Notes | Debt Instrument, Put Option, Period One | Scenario, Forecast                                        
Debt Instrument [Line Items]                                        
Debt instrument, put option, percentage                               100.00%        
Convertible Debt | 2.5% Convertible Senior Notes | Debt Instrument, Redemption, Period One                                        
Debt Instrument [Line Items]                                        
Debt instrument, redemption price, percentage                       100.00%                
Convertible Debt | 3.25% Convertible Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       3.25%                
Aggregate principal amount           $ 117,800,000                            
Bond trading price triggering contingent interest                       $ 1,200                
Individual bond, face value                       $ 1,000                
Debt instrument, contingent interest rate                       0.45%                
Debt instrument, convertible, conversion ratio           0.0131920                            
Debt instrument, convertible, number of equity instruments (in shares) | shares                       1,553,780                
Debt instrument, convertible, discounts and issuance costs, amortization period           7 years                            
Debt instrument, interest rate, effective percentage                       7.20%                
Payments of debt issuance costs           $ 2,500,000                            
Long-term debt, net of discount           95,100,000                            
Debt issuance costs, gross, carrying amount of liability component           2,000,000.0                            
Debt instrument, convertible, carrying amount of equity component           22,700,000                            
Debt issuance costs, gross, carrying amount of equity component           $ 500,000                            
Convertible Debt | 3.25% Convertible Senior Notes | Debt Instrument, Put Option, Period One | Scenario, Forecast                                        
Debt Instrument [Line Items]                                        
Debt instrument, put option, percentage                             100.00%          
Convertible Debt | 3.25% Convertible Senior Notes | Debt Instrument, Redemption, Period One                                        
Debt Instrument [Line Items]                                        
Debt instrument, redemption price, percentage                       100.00%                
Senior Notes | 7.375% Senior Notes                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       7.375%                
Aggregate principal amount                                       $ 250,000,000.0
Debt instrument, repurchased amount         $ 147,400,000                 5,700,000            
Debt extinguishment (gains) losses, net         6,100,000                              
Payments on long-term debt         153,000,000.0                 5,900,000            
Loss on repurchase of debt instrument         $ 5,600,000                              
Line of Credit | SEACOR Revolving Credit Facility                                        
Debt Instrument [Line Items]                                        
Payments of debt issuance costs       $ 2,200,000                                
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility                                        
Debt Instrument [Line Items]                                        
Payments on long-term debt                         25,000,000.0              
Line of credit facility, maximum borrowing capacity       $ 125,000,000.0                                
Line of credit facility, unused capacity, commitment fee percentage                       0.50%                
Proceeds from issuance of long-term debt                       $ 20,000,000.0 $ 25,000,000.0              
Line of credit facility, current borrowing capacity                       $ 105,000,000.0                
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility | Subsequent Event                                        
Debt Instrument [Line Items]                                        
Payments on long-term debt $ 20,000,000.0                                      
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       1.75%                
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       3.00%                
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility | Base Rate | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       0.75%                
Line of Credit | SEACOR Revolving Credit Facility | Revolving Credit Facility | Base Rate | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       2.00%                
Line of Credit | SEA-Vista 2015 Credit Facility                                        
Debt Instrument [Line Items]                                        
Debt extinguishment (gains) losses, net     $ 100,000                                  
Payments of debt issuance costs                 $ 3,100,000                      
Line of credit facility, maximum borrowing capacity                 300,000,000.0                      
Line of Credit | SEA-Vista 2015 Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                         2.00%              
Line of Credit | SEA-Vista 2015 Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                         2.75%              
Line of Credit | SEA-Vista 2015 Credit Facility | Base Rate | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                         1.25%              
Line of Credit | SEA-Vista 2015 Credit Facility | Base Rate | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                         1.75%              
Line of Credit | SEA-Vista 2015 Credit Facility | Revolving Credit Facility                                        
Debt Instrument [Line Items]                                        
Payments on long-term debt                         $ 6,000,000.0 39,000,000.0            
Line of credit facility, maximum borrowing capacity                 100,000,000.0                      
Line of Credit | Sea-Vista 2015 Credit Facility, Term Loan A-1 | Secured Debt                                        
Debt Instrument [Line Items]                                        
Aggregate principal amount                 80,000,000.0                      
Payments on long-term debt                         30,600,000 3,300,000            
Line of Credit | Sea-Vista 2015 Credit Facility, Term Loan A-2 | Secured Debt                                        
Debt Instrument [Line Items]                                        
Aggregate principal amount                 $ 120,000,000.0                      
Payments on long-term debt                         51,400,000 5,500,000            
Line of Credit | SEA-Vista 2019 Credit Facility                                        
Debt Instrument [Line Items]                                        
Payments of debt issuance costs     2,100,000                                  
Line of credit facility, maximum borrowing capacity     200,000,000.0                                  
Line of Credit | SEA-Vista 2019 Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       2.00%                
Line of Credit | SEA-Vista 2019 Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       2.75%                
Line of Credit | SEA-Vista 2019 Credit Facility | Base Rate | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       1.00%                
Line of Credit | SEA-Vista 2019 Credit Facility | Base Rate | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, basis spread on variable rate                       1.75%                
Line of Credit | SEA-Vista 2019 Credit Facility | Revolving Credit Facility                                        
Debt Instrument [Line Items]                                        
Line of credit facility, maximum borrowing capacity     100,000,000.0                                  
Line of credit facility, unused capacity, commitment fee percentage                       0.50%                
Line of credit facility, current borrowing capacity                       $ 100,000,000.0                
Line of Credit | SEA-Vista 2019 Credit Facility, Term Loan [Member] | Secured Debt                                        
Debt Instrument [Line Items]                                        
Aggregate principal amount     100,000,000.0                                  
Payments on long-term debt                       $ 10,000,000.0                
Proceeds from issuance of long-term debt     24,000,000.0                                  
Proceeds from Issuance of Debt to Extinguish Existing Debt     76,000,000.0                                  
Debt instrument, periodic payment, principal, Percent                       2.50%                
Line of Credit | SEA-Vista 2019 Credit Facility, Term Loan [Member] | Secured Debt | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, prepayment increments     $ 1,000,000.0                                  
Line of Credit | ISH Credit Facility                                        
Debt Instrument [Line Items]                                        
Payments of debt issuance costs               $ 100,000                        
Line of credit facility, maximum borrowing capacity               25,000,000.0                        
Line of Credit | ISH Credit Facility | Secured Debt                                        
Debt Instrument [Line Items]                                        
Aggregate principal amount               20,000,000.0                        
Debt extinguishment (gains) losses, net                           (100,000)            
Payments on long-term debt                           $ 12,200,000            
Debt instrument, periodic payment, principal               700,000                        
Line of Credit | ISH Credit Facility | Revolving Credit Facility                                        
Debt Instrument [Line Items]                                        
Line of credit facility, maximum borrowing capacity               $ 5,000,000.0                        
Line of credit facility, unused capacity, commitment fee percentage                           0.50%            
Notes Payable, Other Payables                                        
Debt Instrument [Line Items]                                        
Payments on long-term debt                       $ 900,000 $ 600,000 $ 2,100,000            
Proceeds from Issuance of Debt                       $ 10,600,000                
Notes Payable, Other Payables | ISH Acquired Debt                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                                   7.00%    
Long-term debt acquired in business acquisition                                   $ 3,900,000    
Notes Payable, Other Payables | Weber Acquisition Debt                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                         4.00%              
Long-term debt acquired in business acquisition                         $ 9,900,000              
Notes Payable, Other Payables | Equipment and Facility Mortgages | Minimum                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       3.40%                
Notes Payable, Other Payables | Equipment and Facility Mortgages | Maximum                                        
Debt Instrument [Line Items]                                        
Debt instrument, stated percentage                       6.00%