Annual report pursuant to Section 13 and 15(d)

Note 1 - Nature of Operations and Accounting Policies - Summary of Property and Equipment (Details)

v3.19.1
Note 1 - Nature of Operations and Accounting Policies - Summary of Property and Equipment (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Historical cost $ 1,242,733 [1] $ 1,179,836 [1] $ 958,759
Accumulated depreciation (561,272) (560,160) (540,619)
Net book value 681,461 619,676 $ 418,140
Offshore Support Vessels, Anchor Handling Towing Supply [Member]      
Historical cost [1] 197,343 198,222  
Accumulated depreciation (168,731) (174,159)  
Net book value 28,612 24,063  
Fast Support Vessels [Member]      
Historical cost [1],[2] 404,310 424,865  
Accumulated depreciation [2] (98,580) (89,980)  
Net book value [2] 305,730 334,885  
Offshore Support Vessels, Supply [Member]      
Historical cost [1] 64,284 105,360  
Accumulated depreciation (37,202) (51,494)  
Net book value 27,082 53,866  
Offshore Support Vessels, Standby Safety [Member]      
Historical cost [1] 123,731 118,414  
Accumulated depreciation (97,951) (97,603)  
Net book value 25,780 20,811  
Offshore Support Vessels, Specialty [Member]      
Historical cost [1] 25,683 30,529  
Accumulated depreciation (20,433) (19,304)  
Net book value 5,250 11,225  
Offshore Support Vessels, Liftboats [Member]      
Historical cost [1] 329,473 196,504  
Accumulated depreciation (71,887) (54,161)  
Net book value 257,586 142,343  
Crew Transfer Vessels [Member]      
Historical cost [1] 73,589 65,976  
Accumulated depreciation (46,614) (40,358)  
Net book value 26,975 25,618  
General Machinery and Spares [Member]      
Historical cost [1] 8,457 14,385  
Accumulated depreciation (8,390) (13,244)  
Net book value 67 1,141  
Property, Plant and Equipment, Other Types [Member]      
Historical cost [1],[3] 15,863 25,581  
Accumulated depreciation [3] (11,484) (19,857)  
Net book value [3] $ 4,379 $ 5,724  
[1] Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.
[2] Fast support vessels ("FSVs").
[3] Includes land, buildings, leasehold improvements, vehicles and other property and equipment.