Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (46)	$ (145)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(46)	(145)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	15	78
Derivative, Collateral, Right to Reclaim Cash	7	2
Derivative Liability	(24)	(65)
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	2	7
Derivative Liabilities in Net Liability Positions [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(28)	(68)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(28)	(68)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	9
Derivative, Collateral, Right to Reclaim Cash	7	2
Derivative Liability	(21)	(57)
Derivative liabilities in net asset positions [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(15)	(69)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(15)	(69)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	15	69
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability	0	0
Derivative liabilities with no offsetting arrangements [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(3)	(8)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(3)	(8)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability	(3)	(8)
Securities sold under agreement to repurchase [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(659)	(648)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(659)	(648)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	659	648
Derivative Liability	0	0
Total Derivative Liabilities [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(705)	(793)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	(705)	(793)
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	15	78
Derivative, Collateral, Right to Reclaim Cash	666	650
Derivative Liability	$ (24)	$ (65)