Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Inventory:
Remotely operated vehicle parts and components	$ 105,987		$ 108,939
Other inventory, primarily raw materials	100,684		85,568
Total	206,671		194,507
Other Current Assets:
Prepaid expenses	51,331		60,858
Angolan bonds	10,179		10,179
Total	61,510		71,037
Accrued Liabilities:
Payroll and related costs	116,323		114,676
Accrued job costs	58,227		62,281
Income taxes payable	28,029		34,954
Current operating lease liability	19,733	$ 20,318	0
Other	90,035		95,022
Total	$ 312,347		$ 306,933