Variable Interest Entities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified			12 Months Ended							12 Months Ended			3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2010 Variable Interest Entity, Primary Beneficiary Home Equity	Dec. 31, 2008 Variable Interest Entity, Primary Beneficiary Automobile Loan	Dec. 31, 2010 Variable Interest Entity, Primary Beneficiary Automobile Loan	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary Fifth Third Community Development Corporation Investments [Member]	Dec. 31, 2010 Variable Interest Entity, Primary Beneficiary Fifth Third Community Development Corporation Investments [Member]	Dec. 31, 2011 Variable Interest Entity, Not Primary Beneficiary Loans Receivable	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary Loans Receivable	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary Money Market Funds Upper Limit	Dec. 31, 2011 Variable Interest Entity, Not Primary Beneficiary Fifth Third Community Development Corporation Investments [Member]	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary Fifth Third Community Development Corporation Investments [Member]	Dec. 31, 2011 Variable Interest Entity, Not Primary Beneficiary Private Equity Funds	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary Private Equity Funds	Dec. 31, 2011 Variable Interest Entity, Not Primary Beneficiary Restructured Loans	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary Restructured Loans
Variable Interest Entity [Line Items]
Carry Value Of Loans Leases Or Lines Of Credit Securitized			$ 903	$ 2,700
Number of seperate transactions in which the Bancorp previously sold loans to an isolated trust and conduits					3
Maximum Exposure						10	9				1,243	1,241	327	322	12	13
Equity investments, fair value															0
Equity investments, carrying value	576	522
Unfunded commitment amounts								833	733				166	193	2	1
Capital Contribution To Private Equity Funds													48	34
Credit support										$ 1