Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 80	$ 95
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	80	95
Derivative Asset, Not Subject to Master Netting Arrangement	(7)	(12)
Derivative, Collateral, Obligation to Return Cash	(8)	(9)
Derivative Asset	65	74
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	6	6
Derivative assets in net asset position [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	78	87
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	78	87
Derivative Asset, Not Subject to Master Netting Arrangement	(5)	(4)
Derivative, Collateral, Obligation to Return Cash	(8)	(9)
Derivative Asset	65	74
Derivative assets in net liability positions [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	8
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	2	8
Derivative Asset, Not Subject to Master Netting Arrangement	(2)	(8)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	$ 0	$ 0