Commitments, Contingent Liabilities and Guarantees - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2016		Mar. 31, 2015	Dec. 31, 2015		Dec. 31, 2014	Sep. 30, 2014	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	$ 1,000			$ 1,100
Letters of credit	2,945			3,055
Total Variable Rate Demand Notes	1,200			1,300
Margin account balance held by the brokerage clearing agent	11			10
Amount in excess of amounts reserved	38
Credit loss reserve	1,295	[1]	$ 1,300	1,272	[1]	$ 1,322
Residential Mortgage
Loss Contingencies [Line Items]
Amount in excess of amounts reserved	34
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	23		36	25		$ 35
Outstanding balances on residential mortgage loans sold with credit recourse	$ 451			$ 465
Delinquency Rates	2.60%			3.00%
Credit loss reserve	$ 9			$ 9
Make Whole Payments			1
Repurchased Outstanding Principal	4		9
Repurchase Demand Request	6		$ 9
Outstanding Repurchase Demand Inventory	2			4
Secured Debt
Loss Contingencies [Line Items]
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	62			$ 62
Standby Letters of Credit
Loss Contingencies [Line Items]
Reserve for unfunded commitments	$ 3
Standby letters of credit as a percentage of total letters of credit	99.00%			99.00%
Standby Letters of Credit | Secured Debt
Loss Contingencies [Line Items]
Standby letters of credit as a percentage of total letters of credit	64.00%			65.00%
Variable Rate Demand Note
Loss Contingencies [Line Items]
Letters of credit	$ 185			$ 187
Letters of credit issued by the Bancorp related to variable rate demand notes	841			921
Variable Rate Demand Note | Trading Securities
Loss Contingencies [Line Items]
Total Variable Rate Demand Notes	5
Other Liabilities
Loss Contingencies [Line Items]
Reserve for unfunded commitments	144			138
Other Liabilities | Residential Mortgage
Loss Contingencies [Line Items]
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	23			25
Private Mortgage Reinsurance
Loss Contingencies [Line Items]
Total outstanding reinsurance coverage	27			27
Approximate reserve related to exposures within the reinsurance portfolio	$ 2			2
Private Mortgage Reinsurance | Lower Limit
Loss Contingencies [Line Items]
Reinsurance coverage ranges of the total PMI coverage	5.00%
Private Mortgage Reinsurance | Upper Limit
Loss Contingencies [Line Items]
Reinsurance coverage ranges of the total PMI coverage	10.00%
Visa Litigation
Loss Contingencies [Line Items]
Recorded share of litigation formally settled by Visa and for probable future litigation settlements	$ 55			$ 61
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	$ 150	$ 1,565	$ 400	$ 800	$ 500

[1] Includes $147 and $152 of cash and due from banks, $2,178 and $2,537 of portfolio loans and leases, $(27) and $(28) of ALLL, $11 and $14 of other assets, $4 and $3 of other liabilities, and $2,102 and $2,487 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2016 and December 31, 2015, respectively. For further information refer to Note 9.