Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 3,890	$ 2,229
Accumulated Amortization	1,021	792
Net Carrying Amount	2,869	1,437
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,526	1,970
Accumulated Amortization	824	639
Net Carrying Amount	2,702	1,331
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	364	259
Accumulated Amortization	197	153
Net Carrying Amount	$ 167	$ 106