Long-Term Debt (Uncommitted Funding Facilities) (Details) (Uncommitted Funding Facilities [Member], USD $) In Billions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Outstanding	$ 2.8	$ 7.0
Unused capacity	5.8	2.7
Total capacity	8.6	9.7
Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	1.5	4.8
Unused capacity	5.8	2.2
Total capacity	7.3	7.0
Bank Funding Member | Federal Reserve Bank Advances [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	0	0
Unused capacity	1.8	1.8
Total capacity	1.8	1.8
Bank Funding Member | Federal Home Loan Bank Advances [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	1.5	4.8
Unused capacity	4.0	0.4
Total capacity	5.5	5.2
Nonbank Funding [Member]
Debt Instrument [Line Items]
Outstanding	1.3	2.2
Unused capacity	0	0.5
Total capacity	1.3	2.7
Nonbank Funding [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	0	0.1
Unused capacity	0	0.1
Total capacity	0	0.2
Nonbank Funding [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Outstanding	1.3	2.1
Unused capacity	0	0.4
Total capacity	$ 1.3	$ 2.5