Variable Interest Entities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Private Equity Fund Impairment		$ 4,000,000
Variable Interest Entity, Primary Beneficiary | Automobile Loan Securitizations
Variable Interest Entity [Line Items]
Aggregat Amount of Loans Transferred	3,800,000,000	1,300,000,000
Variable Interest Entity, Primary Beneficiary | Fifth Third Community Development Corporation Investments [Member]
Variable Interest Entity [Line Items]
Maximum Exposure	24,000,000	21,000,000
Variable Interest Entity, Not Primary Beneficiary | Loans Receivable
Variable Interest Entity [Line Items]
Unfunded commitment amounts	859,000,000	962,000,000
Variable Interest Entity, Not Primary Beneficiary | Automobile Loan Securitizations
Variable Interest Entity [Line Items]
Maximum Exposure	2,000,000	4,000,000
Variable Interest Entity, Not Primary Beneficiary | Fifth Third Community Development Corporation Investments [Member]
Variable Interest Entity [Line Items]
Maximum Exposure	1,432,000,000	1,436,000,000
Variable Interest Entity, Not Primary Beneficiary | Private equity investment funds
Variable Interest Entity [Line Items]
Maximum Exposure	267,000,000	294,000,000
Unfunded commitment amounts	78,000,000	90,000,000
Capital Contribution To Private Equity Funds	27,000,000	31,000,000
Variable Interest Entity, Not Primary Beneficiary | Restructured Loans
Variable Interest Entity [Line Items]
Maximum Exposure		$ 1,000,000