VIE (Variable Interest Entities - Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity
Allowance for loan and lease losses	$ 1,196	[1]	$ 1,253	[1]	$ 1,272	$ 1,322
Asset Impairment Charges	277		262
Commercial mortgage loans	6,604		6,899
Private equity investments
Variable Interest Entity
Private Equity Fund Impairment	9		1		0
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity
Allowance for loan and lease losses	6		26
Commercial mortgage loans	20		46
Variable Interest Entity, Primary Beneficiary | Automobile Loans
Variable Interest Entity
Carry Value Of Loans Leases Or Lines Of Credit Securitized	1,100
Face amount of notes issued or redeemed	1,000
Long-term debt reatined	261
Allowance for loan and lease losses	6		6
Commercial mortgage loans	0		0
Variable Interest Entity, Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity
Maximum Exposure	17		31
Allowance for loan and lease losses	0		20
Commercial mortgage loans	20		46
Variable Interest Entity, Not Primary Beneficiary | Loans Provided to VIEs
Variable Interest Entity
Unfunded commitment amounts	1,100		937
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity
Maximum Exposure	1,376		1,421
Bancorp's Investment in Affordable Housing Tax Credits	1,376		1,421
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments | Affordable Housing Investments
Variable Interest Entity
Asset Impairment Charges	(68)
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	1,300		1,300
Unfunded commitments	$ 355		349
Unfunded commitments expected funding date	2034
Variable Interest Entity, Not Primary Beneficiary | Private equity investments
Variable Interest Entity
Maximum Exposure	$ 150		232
Bancorp's Investment in Affordable Housing Tax Credits	102		176
Unfunded commitment amounts	48		56
Capital Contribution To Private Equity Investments	11		14
Variable Interest Entity, Not Primary Beneficiary | Private equity investments | Nonconforming investments affected by Volcker Rule
Variable Interest Entity
Private Equity Fund Impairment	1		$ 9		$ 1
Gain on sale of private equity investments	11
Deconsolidated Variable Interest Entity, Primary Beneficiary | Fifth Third Community Development Corporation Investments
Variable Interest Entity
Maximum Exposure	18
Allowance for loan and lease losses	20
Commercial mortgage loans	$ 27

[1] Includes $ 0 and $ 85 of cash and due from banks, $ 62 and $ 0 of other short-term investments, $ 1,297 and $ 1,216 of portfolio loans and leases, $ (6) and $ (26) of ALLL, $ 7 and $ 9 of other assets, $ 2 and $ 3 of other liabilities and $ 1,190 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2017 and 2016 , respectively. For further information, refer to Note 11 .