Income Taxes (Schedule of Reconciliation of Unrecognized Tax Benefits Included in Uncertain Tax Positions) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Activity Related To Uncertain Tax Positions [Roll Forward]
As of the beginning of the year		$ 134	$ 162	$ 119
Increases in tax positions for the current year		18	1	61
Increases in tax positions for prior years(1)	[1]	26	37	4
Decreases in tax positions for prior years		(13)	(41)	(21)
Decreases due to settlements		0	(25)	(1)
As of the end of the year		165	134	162
Total uncertain tax positions that if recognized would impact the effective tax rate					$ 182	$ 132	$ 154
Total amount of interest expense (benefit) and penalties recognized in the consolidated statements of operations(2)	[2]	6	5	1
Total amount of interest expense and penalties recognized in the consolidated balance sheets					54	45	38
Uncertain tax positions		$ 134	$ 162	$ 162	$ 165	$ 134	$ 162

[1] Includes the impact on uncertain tax positions for the year ended December 31, 2019 due to the closure of federal income tax audits for the years 2009 through 2012.

[2] This amount reflects interest on uncertain tax positions and release of certain tax positions as a result of an audit closure that was reflected in the consolidated statements of operations.