Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 4,194	$ 4,099
Accumulated Amortization	1,607	1,400
Net Carrying Amount	2,587	2,699
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,827	3,713
Accumulated Amortization	1,331	1,170
Net Carrying Amount	2,496	2,543
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	367	386
Accumulated Amortization	276	230
Net Carrying Amount	$ 91	$ 156