Intangible Assets and Goodwill (Intangible Assets and Goodwill) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 378	$ 379
Accumulated Amortization	270	235
Net Carrying Value, Including non-amortizing loan	108	144
Client relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	274	274
Accumulated Amortization	189	169
Net Carrying Value, Including non-amortizing loan	85	105
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	89	89
Accumulated Amortization	66	56
Net Carrying Value, Including non-amortizing loan	23	33
Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	15	16
Accumulated Amortization	15	10
Net Carrying Value, Including non-amortizing loan	$ 0	$ 6