Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 4,025	$ 3,874
Accumulated Amortization	1,314	1,100
Net Carrying Amount	2,711	2,774
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,644	3,494
Accumulated Amortization	1,095	897
Net Carrying Amount	2,549	2,597
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	381	380
Accumulated Amortization	219	203
Net Carrying Amount	$ 162	$ 177