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Exercise price per share or per unit of warrants or rights outstanding.

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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

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This item represents the estimated amount of gains or losses included in earnings during the period attributable to changes in instrument-specific credit risk arising from loans and other receivables held as assets.

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The hypothetical financial impact of a 20 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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Value of loans and leases held in the entity's portfolio transferred to loans and leases held-for-sale in noncash transactions.

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Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2009
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net fair value of the interest rate lock commitments	$ 12
Change in the fair value of the interest rate lock commitments, due to decrease in current interest rates of 25 bp	5
Change in the fair value of the interest rate lock commitments, due to decrease in current interest rates of 50 bp	9
Change in the fair value of the interest rate lock commitments, due to increase in current interest rates of 25 bp	5
Change in the fair value of the interest rate lock commitments, due to increase in current interest rates of 50 bp	11
Change in fair value of interest rate lock commitments, due to 10% adverse changes in the assumed loan closing rates	1
Change in fair value of interest rate lock commitments, due to 20% adverse changes in the assumed loan closing rates	2
Change in fair value of interest rate lock commitments, due to 10% favorable changes in the assumed loan closing rates	1
Change in fair value of interest rate lock commitments, due to 20% favorable changes in the assumed loan closing rates	2
Loans transferred from the portfolio to loans held for sale	855	641	62
Fair value option changes in fair value gain (loss)	26	20
Incremental Unit Purchase Option	20fitb_IncrementalUnitPurchaseOption
Vantiv Holding, LLC Warrant Exercise Price	$ 15.98
Private Equity Fund Impairment		4fitb_PrivateEquityFundImpairment
Vantiv Holding, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants				51.00%
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans transferred from the portfolio to loans held for sale	720
Net impact related to fair value adjustments	87
The fair value of loans	2	2
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net impact related to fair value adjustments	14	26
Nonrecurring losses on loans transferred to OREO	12	19
Commercial Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans transferred from the portfolio to loans held for sale	28	5
Existing loans held for sale, further adjusted	2	3
Net impact related to fair value adjustments	$ 10	$ 4