Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 4,029	$ 2,229
Accumulated Amortization	946	792
Net Carrying Amount	3,083	1,437
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	3,664	1,970
Accumulated Amortization	765	639
Net Carrying Amount	2,899	1,331
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	365	259
Accumulated Amortization	181	153
Net Carrying Amount	$ 184	$ 106