Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 172	$ 167	$ 368	$ 366
Changes in market value of available-for-sale securities:
Unrealized gains (losses), net of taxes of $(4), $2, $0 and $2	(5)	3	1	4
Changes in market value of effective foreign currency forward contracts:
Unrealized gains (losses), net of taxes of $0 for all periods	5	0	(3)	0
Reclassification of (gains) realized during the period, net of taxes of $0 for all periods	(2)	0	0	0
Net change in market value of effective foreign currency forward contracts	3	0	(3)	0
Total other comprehensive income (loss)	(2)	3	(2)	4
Total comprehensive income, net of taxes	$ 170	$ 170	$ 366	$ 370