Commitments, Contingent Liabilities and Guarantees - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified																															3 Months Ended				12 Months Ended					12 Months Ended
	Sep. 30, 2012		Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011	Dec. 31, 2010	Sep. 30, 2012 Residential Mortgage	Dec. 31, 2011 Residential Mortgage	Sep. 30, 2011 Residential Mortgage	Sep. 30, 2012 Standby Letters of Credit	Dec. 31, 2011 Standby Letters of Credit	Sep. 30, 2011 Standby Letters of Credit	Sep. 30, 2012 Standby Letters of Credit Secured Debt	Dec. 31, 2011 Standby Letters of Credit Secured Debt	Sep. 30, 2011 Standby Letters of Credit Secured Debt	Sep. 30, 2012 Variable Rate Demand Note [Member]	Dec. 31, 2011 Variable Rate Demand Note [Member]	Sep. 30, 2011 Variable Rate Demand Note [Member]	Sep. 30, 2012 Other Liabilities	Dec. 31, 2011 Other Liabilities	Sep. 30, 2011 Other Liabilities	Sep. 30, 2012 Private Mortgage Reinsurance	Dec. 31, 2011 Private Mortgage Reinsurance	Sep. 30, 2011 Private Mortgage Reinsurance	Sep. 30, 2012 Private Mortgage Reinsurance Lower Limit	Sep. 30, 2012 Private Mortgage Reinsurance Upper Limit	Sep. 30, 2012 Visa Litigation	Mar. 31, 2012 Visa Litigation	Sep. 30, 2011 Visa Litigation	Jun. 30, 2010 Visa Litigation	Dec. 31, 2011 Visa Litigation	Dec. 31, 2010 Visa Litigation	Dec. 31, 2009 Visa Litigation	Dec. 31, 2008 Visa Litigation	Dec. 31, 2007 Visa Litigation	Dec. 31, 2009 Visa	Dec. 31, 2008 Visa
Commitments and Contingencies Disclosure [Line Items]
Reserve for unfunded commitments														$ 3,000,000	$ 5,000,000	$ 2,000,000							$ 176,000,000	$ 181,000,000	$ 187,000,000
Percentage of the total standby letters of credit														98.00%	98.00%	98.00%	49.00%	54.00%	55.00%
Fifth Third Securities, Inc. (FTS) acted as the remarketing agent to issuers of VRDNs																				2,600,000,000	2,900,000,000	3,000,000,000
Letters of credit	4,558,000,000				4,744,000,000		4,949,000,000													379,000,000	440,000,000	455,000,000
Total outstanding reinsurance coverage																										64,000,000	77,000,000	92,000,000
Approximate reserve related to exposures within the reinsurance portfolio																										21,000,000	27,000,000	28,000,000
Margin account balance held by the brokerage clearing agent	24,000,000				14,000,000		12,000,000
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	800,000,000				2,200,000,000		2,300,000,000
Reinsurance coverage ranges of the total PMI coverage																													5.00%	10.00%
Increase Decrease In Maximum Exposure To Loss																																			54,000,000
Outstanding balances on residential mortgage loans sold with representation and warranty provisions				52,000,000							81,000,000	55,000,000	52,000,000
Outstanding balances on residential mortgage loans sold with credit recourse											687,000,000	772,000,000	828,000,000
Delinquency Rates											6.20%	6.70%	7.30%
Credit loss reserve	1,925,000,000	[1]	2,016,000,000		2,255,000,000	[1]	2,439,000,000	[1]	2,614,000,000	3,004,000,000	18,000,000	17,000,000	17,000,000
Recognized liability equal to the fair value of the indemnification obligation																															50,000,000		31,000,000		49,000,000				3,000,000
Recorded share of litigation formally settled by Visa and for probable future litigation settlements																															21,000,000		27,000,000		78,000,000		29,000,000	71,000,000	169,000,000
Visa IPO, shares of Visa's Class B common stock received																																									10.1
Received Class B common shares, carryover basis																																						3,000,000,000			0
Sale of the Class B shares, recognition of the derivative liability and reversal of the net litigation reserve liability resulted in a pre-tax benefit																																					288,000,000
Sale of the Class B shares, recognition of the derivative liability and reversal of the net litigation reserve liability resulted in an after-tax benefit																																					187,000,000
Free-standing derivative liability initial fair value with reversal of net Visa litigation reserve																																					55,000,000
Visa deposited into the litigation escrow account																															150,000,000		400,000,000	500,000,000	1,565,000,000	800,000,000	700,000,000
Reduction of liability in cash to the swap counterparty																															6,000,000	75,000,000	19,000,000	20,000,000		35,000,000
Share of the Visa escrow account																																						169,000,000
Cash Proceeds Sale Of Stock																																								$ 300,000,000

[1] Includes $0, $30 and $35 of cash, $0, $7 and $7of other short-term investments, $50, $50 and $29 of commercial mortgage loans, $0, $223 and $228 of home equity loans, $0, $259 and $334 of automobile loans, ($2), ($10) and ($10) of ALLL, $3, $4 and $3 of other assets, $0, $4 and $5 of other liabilities, $0, $191and $270 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2012, December 31, 2011 and September 30, 2011, respectively. See Note 8.