Joint Ventures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Joint Ventures
Cash contribution for joint venture	$ 20,000
Additional contribution amount	204,000
Assets:
Accounts receivable	698,477	$ 508,355
Other current assets	180,134	172,019
Property, plant and equipment, net	6,109,565	6,267,583	$ 7,027,802
Other long-term assets	252,854	230,090
Total assets	8,401,984	8,187,015
Liabilities:
Accounts payable	363,416	264,578
Accrued liabilities	533,044	543,248
Total liabilities	5,259,213	$ 4,932,220
SANAD
Assets:
Cash and cash equivalents	94,496
Accounts receivable	10,580
Other current assets	10,834
Property, plant and equipment, net	130,218
Other long-term assets	23,091
Total assets	269,219
Liabilities:
Accounts payable	7,236
Accrued liabilities	2,592
Total liabilities	9,828
Saudi Aramco | SANAD
Joint Ventures
Cash contribution for joint venture	20,000
Additional contribution amount	$ 204,000
Maturity period	25 years
Joint Venture in Saudi Arabia
Joint Ventures
Additional contribution amount	$ 204,000