Related Party (Related Party Transactions - Additional Information) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended														12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016		Dec. 31, 2015	Jun. 30, 2014		Sep. 30, 2013		Jun. 30, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2009	Jun. 30, 2009
Related Party Transactions
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants																				51.00%
Gain on sale of Vantiv, Inc. shares															$ 1,037	$ 0		$ 331
Loans to related parties	$ 20		$ 54												20	54
Letters of Credit	2,185		2,583												2,185	2,583
Taxable Receivable Agreement Payment															44	197		$ 31
Equity investments, carrying value	219		414												219	414
Fair value - Derivative Assets	$ 823		$ 1,057												$ 823	$ 1,057
Vantiv Holding, LLC
Related Party Transactions
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants																				51.00%
Equity Method Investment, Ownership Percentage	8.60%	8.60%	18.30%	[1]	18.30%	22.80%	[1]	25.10%	[1]	27.70%	[1]	33.10%	[1]	39.00%	8.60%	18.30%	[1]	18.30%		49.00%
Gain on sale of Vantiv, Inc. shares		$ 1,037			$ 331	$ 125		$ 85		$ 242		$ 157		$ 115	$ 1,000
Dividend on Equity method investment in Vantiv Holding, LLC															19	$ 9		$ 11
Service fee paid to Vantiv Holding, LLC															72	76		89
Outstanding balance of loans owed to the Bancorp from Vantiv Holding, LLC																			$ 1,250
Loans to related parties	$ 203		$ 210												203	210
Interest income relating to the Vantiv Holding, LLC loans															5	4		$ 4
Letters of Credit	4		$ 59												4	59
Cancellation Of Rights To Purchase Class C Units Under Warrant					4,800,000													4,800,000
Cash Payment For Cancellation Of Warrant					$ 200
Exchange Of Class C Shares For Class A Shares					8,000,000													8,000,000
Investment Warrants Exercise Price			$ 15.98		$ 15.98
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows			$ 171													171
Potential Termination And Settlement Of Tra Cash Flows			394													394
Vantiv Holding, LLC | Interest Rate Contract | Customer Contracts
Related Party Transactions
Fair value - Derivative Assets	$ 2		$ 7												2	7
Vantiv Holding, LLC | Other Noninterest Income
Related Party Transactions
Equity Method Investment, Summarized Financial Information, Net Income (Loss)															47	66		$ 63
Vantiv Holding, LLC | During Deconversion Period
Related Party Transactions
Revenue From Related Parties															1	1		1
Vantiv Holding, LLC | Beyond Deconversion Period
Related Party Transactions
Revenue From Related Parties															$ 68	$ 58		$ 47
Vantiv Holding, LLC | Class B Units
Related Party Transactions
Balance held at close of period in number of shares	35,000,000														35,000,000
Vantiv Holding, LLC | Class C Units
Related Party Transactions
Shares Exercised Underlying Warrant					7,800,000													7,800,000
Warrant Exercised Total Shares Settled			5,700,000		5,400,000											5,700,000		5,400,000
Aggregate amount of each class of warrants or rights outstanding	7,800,000														7,800,000
Vantiv Holding, LLC | Class A Units
Related Party Transactions
Proceeds From Warrant Exercises			$ 9		$ 89
Balance held at close of period in number of shares	35,000,000														35,000,000
Vantiv, Inc.
Related Party Transactions
Gain on sale of Vantiv, Inc. shares	$ 49		116
Voting Power In Vantiv	18.50%														18.50%
Amount Of Cash Flow Sales From 2017 to 2030	$ 140		$ 331													$ 331
Percentage Of Warrant Exercised			62.00%													62.00%
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows	171														$ 171
Potential Termination And Settlement Of Tra Cash Flows	394														394
Pretax Gain Recognized	$ 164														$ 164
Vantiv, Inc. | Minimum
Related Party Transactions
Amount Of Cash Flow Sales From Years 2019 To 2035															2019
Vantiv, Inc. | Upper Limit
Related Party Transactions
Amount Of Cash Flow Sales From Years 2019 To 2035															2035
Vantiv, Inc. | Other Noninterest Income
Related Party Transactions
Taxable Receivable Agreement Payment															$ 44	$ 33		$ 31
Vantiv, Inc. | Class B Units
Related Party Transactions
Shares held in Vantiv, Inc.	43,000,000														43,000,000
Vantiv, Inc. | Class A Units
Related Party Transactions
Exchange Of Class C Shares For Class A Shares			5,700,000		5,400,000											5,700,000		5,400,000
Vantiv, Inc. | Class A Units | Shares Sold In Secondary Offering
Related Party Transactions
Warrant Exercised Total Shares Settled			4,800,000													4,800,000
Vantiv, Inc. | Class A Units | Shares repurchased by Vantiv Inc.
Related Party Transactions
Warrant Exercised Total Shares Settled			900,000													900,000
SLK Global
Related Party Transactions
Equity Method Investment, Ownership Percentage	86.00%														86.00%
Service fee paid to Vantiv Holding, LLC															$ 21	$ 20		$ 17
Equity investments, carrying value	$ 22														22
SLK Global | Other Noninterest Income
Related Party Transactions
Equity Method Investment, Summarized Financial Information, Net Income (Loss)															3
CDC
Related Party Transactions
Loans to related parties	83		$ 76												83	76
Related Party Deposit Liabilities	26		28												26	28
CDC | Unfunded Commitment
Related Party Transactions
Due To Other Related Parties Current And Noncurrent	$ 80		$ 18												$ 80	$ 18

[1] (a) The Bancorp’s remaining investment in Vantiv Holding, LLC of $ 219 as of December 31, 201 7 was accounted for as an equity method investment in the Bancorp’s Consolidated Financial Statements.