Long-Term Debt (Uncommitted Funding Facilities) (Details) (Uncommitted Funding Facilities [Member], USD $) In Billions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Outstanding	$ 7.2	$ 7.0
Unused capacity	3.1	2.7
Total capacity	10.3	9.7
Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	5.0	4.8
Unused capacity	2.6	2.2
Total capacity	7.6	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	4.5	4.8
Unused capacity	0.8	0.4
Total capacity	5.3	5.2
Bank Funding Member | Securities Sold under Agreements to Repurchase [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	0.5	0
Unused capacity	0	0
Total capacity	0.5	0
Nonbank Funding [Member]
Debt Instrument [Line Items]
Outstanding	2.2	2.2
Unused capacity	0.5	0.5
Total capacity	2.7	2.7
Nonbank Funding [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	0	0.1
Unused capacity	0.1	0.1
Total capacity	0.1	0.2
Nonbank Funding [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Outstanding	2.2	2.1
Unused capacity	0.4	0.4
Total capacity	$ 2.6	$ 2.5