Revenue Recognition - Impacts of ASC 606 on Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income	$ 251	$ 221	$ 674	$ 468
Fair market value adjustment on cash flow hedges, net of income tax benefit of $2 million	(4)	1	(5)	3
Foreign currency translation	(6)	6	(6)	11
Total other comprehensive (loss) income	(10)	8	(12)	17
Comprehensive income	241	229	662	485
Income tax provision on fair market value adjustment on cash flow hedges	(2)	1	(2)	2
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income	(23)		(39)
Fair market value adjustment on cash flow hedges, net of income tax benefit of $2 million	0		0
Foreign currency translation	0		0
Total other comprehensive (loss) income	0		0
Comprehensive income	(23)		(39)
Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income	228		635
Fair market value adjustment on cash flow hedges, net of income tax benefit of $2 million	(4)		(5)
Foreign currency translation	(6)		(6)
Total other comprehensive (loss) income	(10)		(12)
Comprehensive income	218		623
Cost of Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 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 $0, $1 million, $1 million and $2 million	(1)	0	(3)	0
Income (benefit) expense on reclassification adjustment for net realized gain on cash flow hedges	0	0	(1)	0
Cost of Services | Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 million	0		0
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $0, $1 million, $1 million and $2 million	0		0
Cost of Services | Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 million	(1)		(3)
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $0, $1 million, $1 million and $2 million	(1)		(3)
Interest Expense
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 million	1	1	2	3
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $0, $1 million, $1 million and $2 million	1	1	2	3
Income (benefit) expense on reclassification adjustment for net realized gain on cash flow hedges	0	$ 1	1	$ 2
Interest Expense | Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 million	0		0
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $0, $1 million, $1 million and $2 million	0		0
Interest Expense | Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reclassification adjustment for net realized gains on cash flow hedges included in cost of processing and services, net of income tax benefit of $0 and $1 million	1		2
Reclassification adjustment for net realized losses on cash flow hedges included in interest expense, net of income tax provision of $0, $1 million, $1 million and $2 million	$ 1		$ 2