Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Customer Resale Agreements [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	$ 462		$ 732
Aggregate Unpaid Principal Balance	430		686
Difference	32		46
Trading Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	22
Aggregate Unpaid Principal Balance	22
Residential mortgage-backed agency securities with embedded derivatives [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value			1,058	[1]
Aggregate Unpaid Principal Balance			864	[1]
Difference			194	[1]
Residential Mortgage Loans Held For Sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	1,477		1,522
Aggregate Unpaid Principal Balance	1,432		1,468
Difference	45		54
Residential Mortgage Loans Held For Sale [Member] | Performing Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	1,430		1,501
Aggregate Unpaid Principal Balance	1,361		1,439
Difference	69		62
Residential Mortgage Loans Held For Sale [Member] | Loans 90 Days Or More Past Due [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	31		19
Aggregate Unpaid Principal Balance	37		25
Difference	(6)		(6)
Residential Mortgage Loans Held For Sale [Member] | Nonaccrual Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	16		2
Aggregate Unpaid Principal Balance	34		4
Difference	(18)		(2)
Commercial Mortgage Loans Held for Sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	811	[2]	843	[2]
Aggregate Unpaid Principal Balance	952	[2]	989	[2]
Difference	(141)	[2]	(146)	[2]
Commercial Mortgage Loans Held for Sale [Member] | Performing Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	805	[2]	829	[2]
Aggregate Unpaid Principal Balance	940	[2]	962	[2]
Difference	(135)	[2]	(133)	[2]
Commercial Mortgage Loans Held for Sale [Member] | Nonaccrual Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	6	[2]	14	[2]
Aggregate Unpaid Principal Balance	12	[2]	27	[2]
Difference	(6)	[2]	(13)	[2]
Residential Mortgage Loans - Portfolio [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	314		227
Aggregate Unpaid Principal Balance	503		368
Difference	(189)		(141)
Residential Mortgage Loans - Portfolio [Member] | Performing Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	83		74
Aggregate Unpaid Principal Balance	114		97
Difference	(31)		(23)
Residential Mortgage Loans - Portfolio [Member] | Loans 90 Days Or More Past Due [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	169	[3]	90	[3]
Aggregate Unpaid Principal Balance	194	[3]	95	[3]
Difference	(25)	[3]	(5)	[3]
Residential Mortgage Loans - Portfolio [Member] | Nonaccrual Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	62		63
Aggregate Unpaid Principal Balance	195		176
Difference	$ (133)		$ (113)

[1] These residential mortgage-backed agency securities with embedded derivatives were carried as Trading securities.

[2] There were no loans 90 days or more past due within this category at September 30, 2012 or December 31, 2011.

[3] The majority of these loans are government insured loans, which positively impacts the fair value.