Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 221	$ 212	$ 468	$ 501
Other comprehensive income (loss):
Fair market value adjustment on cash flow hedges, net of income tax provision of $1 million and $2 million	1	0	3	0
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $1 million, $1 million, $2 million and $2 million	1	1	3	3
Foreign currency translation	6	(6)	11	(3)
Total other comprehensive income (loss)	8	(5)	17	0
Comprehensive income	$ 229	$ 207	$ 485	$ 501