Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 3,823	$ 3,874
Accumulated Amortization	1,160	1,100
Net Carrying Amount	2,663	2,774
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,450	3,494
Accumulated Amortization	951	897
Net Carrying Amount	2,499	2,597
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	373	380
Accumulated Amortization	209	203
Net Carrying Amount	$ 164	$ 177