Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Accounting Policies Earning Per Common Share (Details)

v3.8.0.1
Basis of Presentation and Accounting Policies Earning Per Common Share (Details) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Net income attributable to SEACOR Holdings Inc. $ 641,000 $ 4,083,000
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units 0 0
Dilutive Securities, Effect on Basic Earnings Per Share, Dilutive Convertible Securities 0 0
Net Income Available to Common Stockholders, Diluted $ 641,000 $ 4,083,000
Weighted Average Number of Shares Outstanding, Basic 17,969,970 17,074,043
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements 208,548 289,796
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities 0 0
Weighted Average Number of Shares Outstanding, Diluted 18,178,518 17,363,839
Basic Earnings Per Common Share of SEACOR Holdings Inc. $ 0.04 $ 0.24
Diluted Earnings Per Common Share of SEACOR Holdings Inc. $ 0.04 $ 0.24
Stock Compensation Plan [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 503,459 903,720
Three Point Seven Five Percentage Convertible Notes [Member]    
Debt Instrument, Interest Rate, Stated Percentage 3.75%  
Three Point Seven Five Percentage Convertible Notes [Member] | Convertible Debt Securities [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount   2,243,500
Three Point Zero Percentage Convertible Notes [Member]    
Debt Instrument, Interest Rate, Stated Percentage 3.00%  
Three Point Zero Percentage Convertible Notes [Member] | Convertible Debt Securities [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 2,895,516 1,825,326
Two Point Five Percentage Convertible Notes [Member]    
Debt Instrument, Interest Rate, Stated Percentage 2.50%  
Two Point Five Percentage Convertible Notes [Member] | Convertible Debt Securities [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 1,227,101 1,885,772