Income Taxes (Deferred) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Net operating loss carryforwards	$ 383	$ 365
Tax credit carryforwards	33	23
Accrued payroll expenses not currently deductible	110	128
Deferred income	122	138
Loss contingencies	68	72
Professional fees	3	2
United Kingdom charter limitation	33	69
Other	37	36
Valuation allowance	(412)	(380)
Total deferred tax assets	377	453
Deferred tax liabilities
Depreciation and amortization	(239)	(251)
Other	(18)	(20)
Total deferred tax liabilities	(257)	(271)
Net deferred tax liabilities	120	182
U.S. foreign tax credit carryforwards	33	23
NOLs that are not subject to expiration dates	200	170
NOLs that are subject to expiration dates	183	195
Indefinitely reinvested earnings of subsidiaries	2,500
Estimated taxes on unremitted earnings of subsidiaries, low end of range	200
Estimated taxes on unremitted earnings of subsidiaries, high end of range	250
Reconciliation of unrecognized tax benefits, excluding interest and penalties
Balance, beginning of period	287	272	$ 331
Additions for current year tax positions	42	36	27
Additions for prior year tax positions	13	17	3
Reductions for prior year tax positions	(34)	(27)	(19)
Settlements	(19)	(5)	(47)
Reductions related to statute of limitation expirations	(15)	(6)	(23)
Balance, end of period	274	287	272
Unrecognized tax benefits
Unrecognized tax benefits, excluding interest and penalties	274	287
Interest and penalties	96	118
Unrecognized tax benefits, including interest and penalties	370	405
Interest and penalties related to unrecognized tax benefits recognized as a component of income tax expense	(23)	$ (1)	$ (57)
Amount if recognized that would impact tax rate	$ 370