Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Cost		$ 2,313	$ 2,229
Accumulated Amortization		849	792
Net Carrying Amount		1,464	1,437
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost		2,046	1,970
Accumulated Amortization		685	639
Net Carrying Amount		1,361	1,331
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	[1]	267	259
Accumulated Amortization	[1]	164	153
Net Carrying Amount	[1]	$ 103	$ 106

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