Offsetting Assets and Liabilities (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Offsetting Footnotes [Abstract]
Interest Payable Excluded From Gross Amounts of Derivatives	$ 3,000,000	$ 7,000,000
Securities Borrowed, Transacted Through Clearing Company	34,000,000	278,000,000
Securities Loaned, Transacted Through Clearing Company	722,000,000	1,100,000,000
Derivative Asset, Not Subject to Master Netting Arrangement	10,000,000	0
Derivative Liability, Not Subject to Master Netting Arrangement	44,000,000	36,000,000
Offsetting Assets [Abstract]
Securities Borrowed, Gross	120,000,000	474,000,000
Securities Borrowed, Liability	0	0
Securities Borrowed	120,000,000	474,000,000
Securities Borrowed, Financial Instruments, Not Offset	(94,000,000)	(188,000,000)
Securities Borrowed, Collateral Received	(18,000,000)	(267,000,000)
Securities Borrowed, Amount Offset Against Collateral	8,000,000	19,000,000
Derivative Asset, Fair Value, Gross Asset		24,000,000
Derivative Asset, Fair Value, Gross Liability		0
Derivative Asset		24,000,000
Derivative Asset, Financial Instruments, Not Offset		(15,000,000)
Derivative Asset, Collateral Received		(3,000,000)
Derivative Asset, Fair Value, Amount Offset Against Collateral		6,000,000
Derivative Asset, Securities Borrowed, Gross	120,000,000	498,000,000
Derivative Asset, Securities Borrowed, Liability	0	0
Derivative Asset, Securities Borrowed	120,000,000	498,000,000
Derivative Asset, Securities Borrowed, Financial Instruments Not Offset	(94,000,000)	(203,000,000)
Derivative Asset, Securities Borrowed, Collateral Received	(18,000,000)	(270,000,000)
Derivative Asset, Securities Borrowed Net	8,000,000	25,000,000
Offsetting Liabilities [Abstract]
Securities Loaned, Gross	1,535,000,000	1,649,000,000
Securities Loaned, Asset	0	0
Securities Loaned	1,535,000,000	1,649,000,000
Securities Loaned, Financial Instruments, Not Offset	(94,000,000)	(188,000,000)
Securities Loaned, Collateral Pledged	(1,314,000,000)	(1,332,000,000)
Securities Loaned, Amount Offset Against Collateral	127,000,000	129,000,000
Securities Sold under Agreements to Repurchase, Gross	82,000,000	3,672,000,000
Securities Sold under Agreements to Repurchase, Asset	0	0
Securities sold under agreements to repurchase	82,000,000	3,672,000,000
Securities Sold under Agreements to Repurchase, Financial Instruments Not Offset	0	0
Securities Sold under Agreements to Repurchase, Collateral Pledged	(81,000,000)	(3,671,000,000)
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral	1,000,000	1,000,000
Derivative Liability, Fair Value, Gross Liability	11,000,000	30,000,000
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability	11,000,000	30,000,000
Derivative Liability, Financial Instruments, Not Offset	0	(15,000,000)
Derivative Liability, Collateral Pledged	(11,000,000)	(15,000,000)
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Gross	1,628,000,000	5,351,000,000
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Asset	0	0
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned	1,628,000,000	5,351,000,000
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Financial Instruments Not Offset	(94,000,000)	(203,000,000)
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Collateral Pledged	(1,406,000,000)	(5,018,000,000)
Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Amount Offset Against Collateral	128,000,000	$ 130,000,000
Equity Securities [Member] | Maturity Overnight and Continuous [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Gross Including Not Subject to Master Netting Arrangement	$ 1,500,000,000