Income Taxes (Schedule of Reconciliation of Unrecognized Tax Benefits Included in Uncertain Tax Positions) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Activity Related To Uncertain Tax Positions [Roll Forward]
As of the beginning of the year		$ 162	$ 119	$ 114
Increases in tax positions for the current year		1	61	14
Increases in tax positions for prior years(1)	[1]	37	4	4
Decreases in tax positions for prior years		(41)	(21)	(7)
Decreases due to settlements		(25)	(1)	(6)
As of the end of the year		134	162	119
Total uncertain tax positions that if recognized would impact the effective tax rate					$ 132	$ 154	$ 100
Total amount of interest expense (benefit) and penalties recognized in the consolidated statements of operations(2)	[2]	5	1	6
Total amount of interest expense and penalties recognized in the consolidated balance sheets					45	38	38
Uncertain tax positions		162	$ 119	$ 119	134	$ 162	$ 119
Nilit [Member]
Activity Related To Uncertain Tax Positions [Roll Forward]
As of the end of the year		4
Uncertain tax positions		$ 4			$ 4

[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 and uncertain tax positions related to the Nilit acquisition of $4 million for the year ended December 31, 2017.

[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.