Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 3,982	$ 3,874
Accumulated Amortization	1,221	1,100
Net Carrying Amount	2,761	2,774
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,592	3,494
Accumulated Amortization	1,002	897
Net Carrying Amount	2,590	2,597
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	390	380
Accumulated Amortization	219	203
Net Carrying Amount	$ 171	$ 177