Income Taxes (Reconciliation of Valuation Allowance of Deferred Tax Assets) (Details) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 191	$ 234	$ 350
Change in assessment (a)	1	(2)	1
Current year operations	7	2	(271)
Foreign currency and other	18	(43)	154
Balance at end of year	$ 217	$ 191	$ 234