Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 1,314	$ 1,444	$ 3,969	$ 4,315
Operating Income (Loss)	(447)	(13)	(866)	(125)
Depreciation and Amortization	118	128	357	419
Corporate General and Administrative	31	31	95	101
Goodwill, Impairment Loss	(399)	0	(730)	0	$ 0
Reorganization Items	(303)	0	(303)	0
Prepetition Charges	0	0	(86)	0
Restructuring Charges	(53)	(27)	(93)	(90)
Gain (Loss) on Disposition of Business	(8)	0	104	0
Gain on Operational Assets Sale	15	0	15	0
Western Hemisphere
Segment Reporting Information [Line Items]
Goodwill, Impairment Loss			(508)
Eastern Hemisphere
Segment Reporting Information [Line Items]
Goodwill, Impairment Loss			222
Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,314	1,444	3,969	4,315
Operating Income (Loss)	71	116	139	225
Depreciation and Amortization	117	127	352	413
Operating Segments | Western Hemisphere
Segment Reporting Information [Line Items]
Revenues	675	762	2,120	2,287
Operating Income (Loss)	15	78	35	152
Depreciation and Amortization	44	46	137	162
Operating Segments | Eastern Hemisphere
Segment Reporting Information [Line Items]
Revenues	639	682	1,849	2,028
Operating Income (Loss)	56	38	104	73
Depreciation and Amortization	73	81	215	251
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Depreciation and Amortization	1	1	5	6
Corporate General and Administrative	31	31	95	101
Segment Reconciling Items
Segment Reporting Information [Line Items]
Goodwill, Impairment Loss			(730)
Prepetition Charges			(86)
Restructuring Charges	(53)	(27)	(93)	90
Impairment of Long-Lived Assets and Other Related Charges	(42)	$ 71	120	$ 159
Gain (Loss) on Disposition of Business	$ (8)
Gain on Operational Assets Sale			$ 104