Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Variable Interest Entity, Primary Beneficiary | Automobile Loan [Member]
Variable Interest Entity [Line Items]
Carry Value Of Loans Leases Or Lines Of Credit Securitized						$ 3,800
Variable Interest Entity, Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity [Line Items]
Maximum Exposure	$ 26			$ 26		24
Variable Interest Entity, Not Primary Beneficiary | Loans Receivable
Variable Interest Entity [Line Items]
Unfunded commitment amounts	1,100			1,100		859
Variable Interest Entity, Not Primary Beneficiary | Automobile Loan [Member]
Variable Interest Entity [Line Items]
Carry Value Of Loans Leases Or Lines Of Credit Securitized			$ 509
Maximum Exposure	1			1		2
Total Assets	1			1		2
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity [Line Items]
Maximum Exposure	1,447			1,447		1,432
Total Assets	1,447			1,447		1,432
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments | Qualified Affordable Housing Tax Credits
Variable Interest Entity [Line Items]
Total Assets	1,300			1,300		1,300
Unfunded commitments	356			$ 356		357
Unfunded commitments expected funding date				2031
Variable Interest Entity, Not Primary Beneficiary | Private Equity Funds
Variable Interest Entity [Line Items]
Maximum Exposure	271			$ 271		267
Total Assets	211			211		189
Unfunded commitment amounts	60			60		$ 78
Capital Contribution To Private Equity Funds	$ 6	$ 8		$ 28	$ 20