Income Taxes (Schedule of Reconciliation of Unrecognized Tax Benefits Included in Uncertain Tax Positions) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits		$ 119	$ 114	$ 158	$ 162	$ 119	$ 114
As of the beginning of the year		119	114	158
Increases in tax positions for the current year		61	14	9
Increases in tax positions for prior years(1)	[1]	4	4	11
Decreases in tax positions for prior years		(21)	(7)	(9)
Decreases due to settlements		(1)	(6)	(55)
As of the end of the year		162	119	114
Total uncertain tax positions that if recognized would impact the effective tax rate					154	100	87
Total amount of interest expense (benefit) and penalties recognized in the consolidated statements of operations(2)	[2]	1	$ 6	$ (16)
Total amount of interest expense and penalties recognized in the consolidated balance sheets					38	$ 38	$ 26
Nilit [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits		4			$ 4
As of the end of the year		$ 4

[1] Includes uncertain tax positions related to the Nilit acquisition (Note 4) of $4 million for the year ended December 31, 2018.

[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.