Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 41	$ 95
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	41	95
Derivative Asset, Not Subject to Master Netting Arrangement	(1)	(12)
Derivative, Collateral, Obligation to Return Cash	0	(9)
Derivative Asset	40	74
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	3	6
Derivative assets in net asset position [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	39	87
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	39	87
Derivative Asset, Not Subject to Master Netting Arrangement	0	(4)
Derivative, Collateral, Obligation to Return Cash	0	(9)
Derivative Asset	39	74
Derivative assets in net liability positions [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	8
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	8
Derivative Asset, Not Subject to Master Netting Arrangement	(1)	(8)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	$ 0	$ 0