Segment Information - Schedule of Reconciliation of Reportable Segment Depreciation and Amortization Amounts to the Consolidated Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Amortization of initial payments for new contracts	$ 16	$ 14	$ 47	$ 38
Total consolidated depreciation and amortization per unaudited consolidated statements of cash flows	265	286	793	843
Amortization of equity method investments	(12)	(15)	(33)	(45)
Amortization of initial payments for new contracts	(16)	(14)	(47)	(38)
Total consolidated depreciation and amortization per unaudited consolidated statements of operations	237	257	713	760
Operating Segments
Segment Reporting Information [Line Items]
Segment depreciation and amortization	231	252	690	743
Segment Reconciling Items
Segment Reporting Information [Line Items]
Adjustments for non wholly owned entities	18	20	56	62
Amortization of initial payments for new contracts	16	14	47	38
Amortization of equity method investments	(12)	(15)	(33)	(45)
Amortization of initial payments for new contracts	(16)	(14)	(47)	(38)
Total consolidated depreciation and amortization per unaudited consolidated statements of operations	$ (237)	$ (257)	$ (713)	$ (760)