Income Taxes (Deferred) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforwards				$ 571	$ 479
Interest expense limitation				77	76
Accrued payroll expenses not currently deductible				45	49
Deferred income				41	26
Loss contingencies				38	40
United Kingdom charter limitation				36	30
Tax credit carryforwards				22	11
Accrued expenses				16	44
Other				24	13
Valuation allowance				(716)	(681)
Total deferred tax assets				154	87
Deferred tax liabilities
Depreciation				(361)	(62)
Contract intangible amortization				(23)	(22)
Other				(16)	(1)
Total deferred tax liabilities				(400)	(85)
Net deferred tax liabilities				(246)
Net deferred tax assets					2
U.S. foreign tax credit carryforwards				22	11
NOLs that are not subject to expiration dates				354	307
NOLs that are subject to expiration dates				217	172
Indefinitely reinvested earnings				254
Unrecognized deferred tax liability on indefinitely reinvested earnings				13
Reconciliation of unrecognized tax benefits, excluding interest and penalties
Balance, beginning of period	$ 408	$ 222	$ 274
Additions for prior year tax positions	6	172	17
Additions for current year tax positions	144	29	13
Reductions related to statute of limitation expirations and changes in law	(138)	(8)	(13)
Reductions for prior year tax positions	(66)	(7)	(68)
Reductions due to settlements	(19)		(1)
Balance, end of period	335	408	222
Unrecognized tax benefits
Unrecognized tax benefits, excluding interest and penalties	335	222	222	335	408
Interest and penalties				34	106
Unrecognized tax benefits, including interest and penalties				369	$ 514
Interest and penalties related to unrecognized tax benefits recognized as a component of income tax expense	$ (72)	$ 13	$ (9)
Amount if recognized that would impact tax rate				$ 175