Derivative Financial Instruments (Narrative) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Derivative [Line Items]
Cash collateral received for derivative instruments	$ 2,870,000,000		$ 1,680,000,000
Cash collateral provided for derivative instruments	2,800,000,000		1,300,000,000
Fair value of derivative liabilities	10,577,000,000	[1]	9,438,000,000	[1]
Weighted average life of trusts (in years)	6 years 8 months		6 years 11 months
Credit swap agreements
Derivative [Line Items]
Fair value of derivative liabilities	421,000,000
Carrying value of the underlying collateral	0
Maximum additional amount of payments related to termination events	$ 421,000,000
Fair Value Hedges | Interest rate swap | Senior notes
Derivative [Line Items]
Number of securities	1
Fair Value Hedges | Interest rate swap | Subordinated note
Derivative [Line Items]
Number of securities	1
Fair Value Hedges | 1.35% Senior Note
Derivative [Line Items]
Fixed interest rate	1.35%
Fair Value Hedges | 3.1% Subordinated Note | Interest rate swap
Derivative [Line Items]
Fixed interest rate	3.10%
Cash Flow Hedges
Derivative [Line Items]
Securities weighted average life (in years)	1 year		1 year 9 months

[1] Amounts include all transactions regardless of whether or not they are subject to an enforceable netting arrangement.