Segment Information - Schedule of Reconciliation of Reportable Segment Depreciation and Amortization Amounts to the Consolidated Balances (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Amortization of initial payments for new contracts	$ 16	$ 13	$ 31	$ 24
Total consolidated depreciation and amortization per unaudited consolidated statements of cash flows	266	280	528	557
Amortization of equity method investments	(12)	(15)	(21)	(30)
Amortization of initial payments for new contracts	(16)	(13)	(31)	(24)
Total consolidated depreciation and amortization per unaudited consolidated statements of operations	238	252	476	503
Operating Segments
Segment Reporting Information [Line Items]
Segment depreciation and amortization	231	246	459	491
Segment Reconciling Items
Segment Reporting Information [Line Items]
Adjustments for non wholly owned entities	19	21	38	42
Amortization of initial payments for new contracts	16	13	31	24
Amortization of equity method investments	(12)	(15)	(21)	(30)
Amortization of initial payments for new contracts	(16)	(13)	(31)	(24)
Total consolidated depreciation and amortization per unaudited consolidated statements of operations	$ (238)	$ (252)	$ (476)	$ (503)