Segment Information - Geographical (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	$ 17,663	$ 17,549
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	16,507	16,094
EQUATORIAL GUINEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	1,156	1,333
Other International
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	$ 0	$ 122