Annual report pursuant to Section 13 and 15(d)

Business Acquisitions (Details)

v3.8.0.1
Business Acquisitions (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
equipment
Dec. 31, 2016
USD ($)
equipment
Jul. 03, 2017
USD ($)
Dec. 02, 2016
Dec. 31, 2015
USD ($)
Business Acquisition [Line Items]          
Restricted cash $ 13 $ 0     $ 0
Trade and other receivables 15,823 937     0
Other current assets 2,054 150     0
Investments, at Equity, and Advances to 50% or Less Owned Companies 10,000 (3,437)     0
Property and Equipment 15,190 15,765     0
Goodwill 0 0     3,157
Intangible Assets 10,957 7,098     (3,157)
Other Assets (17,863) 0     0
Accounts payable 0 39     0
Other current liabilities (17,214) (13)     0
Long-Term Debt (28,725) 0     0
Deferred Income Taxes (3,939)        
Deferred Income Taxes, Noncurrent   0     0
Other Liabilities (42) 0     0
Purchase price (5,868) 20,539     $ 0
Cash Acquired from Acquisition $ 16,400 900      
Central Contracting & Marine, Inc. [Member]          
Business Acquisition [Line Items]          
Payments to Acquire Businesses, Gross   18,100      
SeaJon II [Member]          
Business Acquisition [Line Items]          
Business Acquisition, Percentage of Voting Interests Acquired       50.00%  
Payments to Acquire Businesses, Gross   $ 3,400      
Inland River Harbor Boats [Member] | Central Contracting & Marine, Inc. [Member]          
Business Acquisition [Line Items]          
Number Of Equipments Acquired | equipment 5 5      
U.S-flag Offshore Tug [Member] | SeaJon II [Member]          
Business Acquisition [Line Items]          
Number Of Equipments Acquired | equipment   1      
ISH [Member]          
Business Acquisition [Line Items]          
Payments to Acquire Businesses, Gross $ 10,500        
Debt Conversion, Converted Instrument, Amount $ 18,100        
Long-Term Debt     $ (28,700)