Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Cost		$ 1,910	$ 1,594
Accumulated Amortization		590	468
Net Carrying Amount		1,320	1,126
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost		1,679	1,390
Accumulated Amortization		487	392
Net Carrying Amount		1,192	998
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Cost	[1]	231	204
Accumulated Amortization	[1]	103	76
Net Carrying Amount	[1]	$ 128	$ 128

[1] Primarily non-compete agreements, trade names and developed technology.