Commitments, Contingent Liabilities and Guarantees - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Sep. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Mar. 31, 2013		Dec. 31, 2012		Dec. 31, 2007
Commitments and Contingencies Disclosure
Letters of credit									$ 4,191,000,000		$ 4,281,000,000
Margin account balance held by the brokerage clearing agent									12,000,000		17,000,000
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities									800,000,000		800,000,000
Credit loss reserve		2,126,000,000			2,255,000,000				1,783,000,000	[1]	1,854,000,000	[1]
Residential Mortgage
Commitments and Contingencies Disclosure
Outstanding balances on residential mortgage loans sold with representation and warranty provisions									112,000,000		110,000,000
Outstanding balances on residential mortgage loans sold with credit recourse									630,000,000		662,000,000
Delinquency Rates									5.20%		5.90%
Credit loss reserve									21,000,000		20,000,000
Maximum Reasonably Possible Loss Related To Mortgage Representation And Warranty Provisions In Excess Of Reserve									89,000,000
Standby Letters of Credit
Commitments and Contingencies Disclosure
Reserve for unfunded commitments									2,000,000		4,000,000
Percentage of the total standby letters of credit									98.00%		99.00%
Standby Letters of Credit | Secured Debt
Commitments and Contingencies Disclosure
Percentage of the total standby letters of credit									49.00%		49.00%
Variable Rate Demand Note
Commitments and Contingencies Disclosure
Fifth Third Securities, Inc. (FTS) acted as the remarketing agent to issuers of VRDNs									2,400,000,000		2,500,000,000
Letters of credit									343,000,000		345,000,000
Other Liabilities
Commitments and Contingencies Disclosure
Reserve for unfunded commitments									168,000,000		179,000,000
Private Mortgage Reinsurance
Commitments and Contingencies Disclosure
Total outstanding reinsurance coverage									56,000,000		58,000,000
Approximate reserve related to exposures within the reinsurance portfolio									16,000,000		18,000,000
Private Mortgage Reinsurance | Lower Limit
Commitments and Contingencies Disclosure
Reinsurance coverage ranges of the total PMI coverage									5.00%
Private Mortgage Reinsurance | Upper Limit
Commitments and Contingencies Disclosure
Reinsurance coverage ranges of the total PMI coverage									10.00%
Visa Litigation
Commitments and Contingencies Disclosure
Increase Decrease In Maximum Exposure To Loss					54,000,000
Recognized liability equal to the fair value of the indemnification obligation													3,000,000
Recorded share of litigation formally settled by Visa and for probable future litigation settlements							29,000,000	71,000,000	37,000,000		33,000,000		169,000,000
Received Class B common shares, carryover basis								3,000,000,000
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
Visa
Commitments and Contingencies Disclosure
Visa IPO, shares of Visa's Class B common stock received								10.1
Received Class B common shares, carryover basis								0
Cash Proceeds Sale Of Stock							$ 300,000,000

[1] Includes $50 and $50 of commercial mortgage loans, $(13) and $(5) of ALLL, $1 and $3 of other assets from consolidated VIEs that are included in their respective captions above at March 31, 2013 and December 31, 2012, respectively. See Note 8.