Commitments, Contingent Liabilities and Guarantees - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended			9 Months Ended			12 Months Ended
	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014		Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Loss Contingencies [Line Items]
Fifth Third Securities, Inc. (FTS) acted as the remarketing agent to issuers of VRDNs	$ 1,100			$ 1,100			$ 1,400
Letters of credit	3,323			3,323			3,974
Total Variable Rate Demand Notes	1,400			1,400			1,700
Margin account balance held by the brokerage clearing agent	11			11			13
Amount in excess of amounts reserved	51			51
Credit loss reserve	1,261	[1]	$ 1,414	1,261	[1]	$ 1,414	1,322	[1]	$ 1,293	$ 1,458	$ 1,582
Residential Mortgage
Loss Contingencies [Line Items]
Amount in excess of amounts reserved	21			21
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	28		35	28		35	35		$ 32	$ 36	$ 44
Outstanding balances on residential mortgage loans sold with credit recourse	$ 464			$ 464			$ 548
Delinquency Rates	3.30%			3.30%			4.00%
Credit loss reserve	$ 10			$ 10			$ 11
Make Whole Payments			1	2		10
Repurchased Outstanding Principal	7		7	64		47
Repurchase Demand Request	7		24	68		84
Outstanding Repurchase Demand Inventory				4			7
Secured Debt
Loss Contingencies [Line Items]
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	$ 62			$ 62			62
Standby Letters of Credit
Loss Contingencies [Line Items]
Reserve for unfunded commitments							$ 1
Standby letters of credit as a percentage of total letters of credit	98.00%			98.00%			97.00%
Standby Letters of Credit | Secured Debt
Loss Contingencies [Line Items]
Standby letters of credit as a percentage of total letters of credit	64.00%			64.00%			60.00%
Variable Rate Demand Note
Loss Contingencies [Line Items]
Letters of credit	$ 220			$ 220			$ 247
Letters of credit issued by the Bancorp related to variable rate demand notes	971			971			1,200
Other Liabilities
Loss Contingencies [Line Items]
Reserve for unfunded commitments	134			134			135
Other Liabilities | Residential Mortgage
Loss Contingencies [Line Items]
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	28			28			35
Private Mortgage Reinsurance
Loss Contingencies [Line Items]
Total outstanding reinsurance coverage	27			27			29
Approximate reserve related to exposures within the reinsurance portfolio	$ 2			$ 2			2
Private Mortgage Reinsurance | Lower Limit
Loss Contingencies [Line Items]
Reinsurance coverage ranges of the total PMI coverage	5.00%			5.00%
Private Mortgage Reinsurance | Upper Limit
Loss Contingencies [Line Items]
Reinsurance coverage ranges of the total PMI coverage	10.00%			10.00%
Visa Litigation
Loss Contingencies [Line Items]
Recorded share of litigation formally settled by Visa and for probable future litigation settlements	$ 58			$ 58			$ 49
Visa deposited into the litigation escrow account																	$ 3
Visa
Loss Contingencies [Line Items]
Visa IPO, shares of Visa's Class B common stock received																	10.1
Visa deposited into the litigation escrow account			$ 450			$ 450						$ 150	$ 1,565	$ 400	$ 800	$ 500

[1] Includes $137 and $179 of cash and due from banks, $2,179 and $3,378 of portfolio loans and leases, $(27) and $(22) of ALLL, $18 and $25 of other assets, $3 and $5 of other liabilities, and $2,136 and $3,434 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2015 and December 31, 2014, respectively. For further information refer to Note 11.