Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Provision for income taxes for discontinued operations	$ 38	$ 32	$ 47
(Provision) benefit for income taxes	(535)	29	(580)
Net deferred tax assets of discontinued operations	93	76
Net operating loss carryforwards	2,060
Valuation allowance	593	547
Provisional amount of transition tax on cumulative foreign earnings and profits			48
Decrease for reserve for uncertain tax positions		146
Unrecognized tax benefits	308	384	446	$ 300
Amount included in reserve for uncertain tax positions that would affect Company's effective income tax rate (including discontinued operations) if recognized	281
Interest and penalty charges related to the reserve for uncertain tax positions	16	24	24
Liabilities for accrued interest and penalty charges related to the reserve for uncertain tax positions	57	51
Amount of unrecorded benefit	50
Foreign [Member]
Related Party Transaction [Line Items]
Net operating loss carryforwards	29
Equity Method Investees [Member]
Related Party Transaction [Line Items]
(Provision) benefit for income taxes	$ 19	$ 19	$ 15
Effective income tax rate	40.40%	26.40%	24.20%