Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Inventory:
Remotely operated vehicle parts and components	$ 114,059		$ 108,939
Other inventory, primarily raw materials	88,951		85,568
Total	203,010		194,507
Other Current Assets:
Prepaid expenses	62,534		60,858
Angolan bonds	10,179		10,179
Total	72,713		71,037
Accrued Liabilities:
Payroll and related costs	96,257		114,676
Accrued job costs	71,662		62,281
Income taxes payable	24,435		34,954
Current operating lease liability	20,001	$ 20,318	0
Other	97,547		95,022
Total	$ 309,902		$ 306,933