Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 141	$ 233
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	141	233
Derivative Asset, Not Subject to Master Netting Arrangement	(16)	(78)
Derivative, Collateral, Obligation to Return Cash	(104)	(67)
Derivative Asset	21	88
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	2	7
Derivative assets in net liability positions [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	9
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	9
Derivative Asset, Not Subject to Master Netting Arrangement	(1)	(9)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	0	0
Derivative assets in net asset position [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	140	224
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	140	224
Derivative Asset, Not Subject to Master Netting Arrangement	(15)	(69)
Derivative, Collateral, Obligation to Return Cash	(104)	(67)
Derivative Asset	$ 21	$ 88