Derivative Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Derivative [Line Items]
Cash collateral received for derivative instruments	$ 2,420,000,000		$ 1,680,000,000
Cash collateral provided for derivative instruments	1,970,000,000		1,300,000,000
Fair value of derivative liabilities	4,778,000,000	[1]	4,399,000,000	[1]
Weighted average life of trusts (in years)	6 years 8 months 12 days		6 years 11 months
Credit swap agreements
Derivative [Line Items]
Fair value of derivative liabilities	850,000,000
Collateral already posted, aggregate fair value	130,000,000
Maximum additional amount of payments related to termination events	$ 720,000,000
Fair Value Hedges | 4.375% Senior Note
Derivative [Line Items]
Fixed interest rate	4.375%
Cash Flow Hedges
Derivative [Line Items]
Securities weighted average life (in years)	1 year 6 months		1 year 9 months 18 days

[1] In addition to the $183 million and $328 million as of March 31, 2013 and December 31, 2012, respectively, we have $5,187 million and $5,039 million, respectively, of derivative liabilities not determined to be subject to enforceable netting arrangements. Refer to notes 2 and 10 for additional information with respect to derivative financial instrument balances recorded in our consolidated statement of condition.