Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Cost		$ 1,948	$ 1,906
Accumulated Amortization		714	632
Net Carrying Amount		1,234	1,274
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost		1,711	1,672
Accumulated Amortization		580	518
Net Carrying Amount		1,131	1,154
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Cost	[1]	237	234
Accumulated Amortization	[1]	134	114
Net Carrying Amount	[1]	$ 103	$ 120

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