VIE (Variable Interest Entities - Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Variable Interest Entity
OTTI	[1]	$ 14	$ 3	$ 24	$ 5
Variable Interest Entity, Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity
Maximum Exposure		34		34		$ 31
Variable Interest Entity, Not Primary Beneficiary | Loans Provided to VIEs
Variable Interest Entity
Unfunded commitment amounts		940		940		937
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity
Maximum Exposure		1,495		1,495		1,421
Bancorp's Investment in Affordable Housing Tax Credits		1,495		1,495		1,421
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments | Qualified Affordable Housing Tax Credits
Variable Interest Entity
Bancorp's Investment in Affordable Housing Tax Credits		1,400		1,400		1,300
Unfunded commitments		$ 412		412		349
Unfunded commitments expected funding date		2034
Variable Interest Entity, Not Primary Beneficiary | Private Equity Investments
Variable Interest Entity
Maximum Exposure		$ 170		170		232
Bancorp's Investment in Affordable Housing Tax Credits		116		116		176
Unfunded commitment amounts		54		54		$ 56
Capital Contribution To Private Equity Investments			6	7	8
OTTI		$ 0	$ 0	$ 0	$ 0

[1] (a) Included in securities gains, net in the Condensed Consolidated Statements of Income.