Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 807	$ 1,314	$ 2,843	$ 3,969
Operating Income (Loss)	(60)	(447)	(1,379)	(866)
Other Cost and Expense, Operating	(16)	(42)	(48)	(100)
(Gain) Loss on Sale of Businesses, Net	0	8	0	(104)
Interest Expense, Net (Unrecognized Contractual Interest Expense was $133 million for three and nine months ended September 30, 2019)	79	26	196	341
Reorganization Items	0	(303)	(9)	(303)
Other Expense, Net	(20)	(8)	(56)	(18)
Loss Before Income Taxes	(159)	(784)	(1,640)	(1,528)
Total Assets	5,664		5,664		$ 7,293
Gain (Loss) on Disposition of Assets	12	15	12	15
Operating Segments
Segment Reporting Information [Line Items]
Revenue	807	1,314	2,843	3,969
Operating Income (Loss)	3	71	42	139
Other Cost and Expense, Operating	(47)	(494)	(1,353)	(1,029)
Operating Segments | Western Hemisphere
Segment Reporting Information [Line Items]
Revenue	316	675	1,214	2,120
Operating Income (Loss)	(2)	15	4	35
Total Assets	1,694		1,694		2,514
Operating Segments | Eastern Hemisphere
Segment Reporting Information [Line Items]
Revenue	491	639	1,629	1,849
Operating Income (Loss)	5	56	38	104
Total Assets	3,264		3,264		4,392
Corporate, Non-Segment
Segment Reporting Information [Line Items]
General and Administrative Expense	(28)	$ (31)	(80)	$ (95)
Total Assets	$ 706		$ 706		$ 387