Segment Information - Geographical (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 5,888	$ 4,373	$ 3,170
Long-Lived Assets	17,549	18,512
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	4,872	3,086	2,400
Long-Lived Assets	16,094	15,955
EQUATORIAL GUINEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	383	530	444
Long-Lived Assets	1,333	1,598
LIBYAN ARAB JAMAHIRIYA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	196	431	54
U.K.
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	360	289	263
Other International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	77	37	$ 9
Long-Lived Assets	$ 122	$ 959