Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Variable Interest Entity, Primary Beneficiary | Automobile Loan Securitizations
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	1,200			1,200		859
Variable Interest Entity, Not Primary Beneficiary | Automobile Loan Securitizations
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	1,432			1,432		1,432
Total Assets	1,432			1,432		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	359			$ 359		357
Unfunded commitments expected funding date				2031
Variable Interest Entity, Not Primary Beneficiary | Private Equity Funds
Variable Interest Entity [Line Items]
Maximum Exposure	275			$ 275		267
Total Assets	209			209		189
Unfunded commitment amounts	66			66		$ 78
Capital Contribution To Private Equity Funds	$ 12	$ 5		$ 22	$ 12