Goodwill and Other Intangibles - Components of Other Intangibles (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Cost	$ 7,399	$ 7,435
Accumulated Amortization	(5,660)	(5,299)
Net of Accumulated Amortization	1,739	2,136
Conversion costs
Finite-Lived Intangible Assets [Line Items]
Cost	248	218
Accumulated Amortization	(109)	(102)
Net of Accumulated Amortization	139	116
Contract costs
Finite-Lived Intangible Assets [Line Items]
Cost	306	280
Accumulated Amortization	(149)	(123)
Net of Accumulated Amortization	157	157
Software
Finite-Lived Intangible Assets [Line Items]
Cost	2,236	2,019
Accumulated Amortization	(1,726)	(1,547)
Net of Accumulated Amortization	510	472
Other, including trade names
Finite-Lived Intangible Assets [Line Items]
Cost	1,375	1,400
Accumulated Amortization	(381)	(362)
Net of Accumulated Amortization	994	1,038
Total other intangibles
Finite-Lived Intangible Assets [Line Items]
Cost	4,165	3,917
Accumulated Amortization	(2,365)	(2,134)
Net of Accumulated Amortization	$ 1,800	$ 1,783