Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 232	$ 214	$ 700	$ 715
Other comprehensive income (loss):
Fair market value adjustment on cash flow hedges, net of income tax (benefit) provision of $(1) million and $1 million	(1)	0	2	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, $3 million and $3 million	2	2	5	5
Foreign currency translation	3	3	14	0
Total other comprehensive income	4	5	21	5
Comprehensive income	$ 236	$ 219	$ 721	$ 720