Variable Interest Entities - Summary of Assets and Liabilities Related to Consolidated Variable Interest Entities (Details) (USD $)	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012
Variable Interest Entity [Line Items]
Interest bearing deposits with banks	$ 29,820,000,000		$ 13,279,000,000
Securities held-to-maturity	1,538,000,000		1,620,000,000
Other assets	8,765,000,000		7,069,000,000
Short-term borrowings	21,394,000,000		14,933,000,000
Long-term debt	20,934,000,000		21,745,000,000
Other	5,584,000,000		4,562,000,000
Total assets	192,386,000,000	[1]	196,567,000,000	[1]	200,427,000,000
Total liabilities	174,984,000,000	[1]	178,731,000,000	[1]
Variable interest entities
Variable Interest Entity [Line Items]
Interest bearing deposits with banks	221,000,000		216,000,000
Securities held-to-maturity	218,000,000		0
Other assets	544,000,000		533,000,000
Short-term borrowings	400,000,000		0
Long-term debt	92,000,000		92,000,000
Other	122,000,000		152,000,000
Total assets	983,000,000		749,000,000
Total liabilities	614,000,000		244,000,000
Asset-backed commercial paper conduits [Member]
Variable Interest Entity [Line Items]
Interest bearing deposits with banks	8,000,000		0
Securities held-to-maturity	218,000,000		0
Other assets	49,000,000		0
Short-term borrowings	400,000,000		0
Other	3,000,000		0
Total assets	275,000,000		0
Total liabilities	403,000,000		0
Low Income Housing Limited Liability Partnership [Member]
Variable Interest Entity [Line Items]
Interest bearing deposits with banks	213,000,000		216,000,000
Other assets	495,000,000		533,000,000
Long-term debt	92,000,000		92,000,000
Other	119,000,000		152,000,000
Total assets	708,000,000		749,000,000
Total liabilities	$ 211,000,000		$ 244,000,000

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities (“VIEs”) as of June 30, 2013 and 2012 which are consolidated on our balance sheet. Assets and liabilities exclude intercompany balances that eliminate in consolidation. Assets: Interest bearing deposits with banks, $221 and $216, Other assets $544 and $533, Total assets $983 and $749 respectively. Liabilities: Long-term debt $92 and $92, Interest, taxes and other liabilities $122 and $152. Total liabilities $614 and $244, respectively.