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Related Party (Related Party Transactions - Additional Information) (Detail) - USD ($) $ in Millions	3 Months Ended										12 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2010	Sep. 30, 2017	Jun. 30, 2009
Related Party Transactions
Equity Method Investment, Ownership Percentage	0.00%	3.30%	4.90%													8.60%
Gain on sale of Worldpay, Inc. shares	$ 562	$ 205	$ 414								$ 562	$ 205	$ 1,037
Loans to related parties											49	10
Taxable Receivable Agreement Payment											346	20	44
Equity investments, carrying value											0	420
Other Noninterest Income
Related Party Transactions
Gain on sale of Worldpay, Inc. shares				$ 116
Taxable Receivable Agreement Payment											1	20	44
Worldpay Holding, LLC
Related Party Transactions
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants																	51.00%
Equity Method Investment, Ownership Percentage					18.30%	22.80%	25.10%	27.70%	33.10%	39.00%				18.30%			49.00%
Gain on sale of Worldpay, Inc. shares					$ 331	$ 125	$ 85	$ 242	$ 157	$ 115
Dividend on Equity method investment in Vantiv Holding, LLC											1	3	19
Service fee paid to Vantiv Holding, LLC											77	74	72
Outstanding balance of loans owed to the Bancorp from Vantiv Holding, LLC															$ 1,250
Loans to related parties												187
Interest income relating to the Vantiv Holding, LLC loans											2	7	5
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows				171
Membership Units	10,252,826
Worldpay Holding, LLC \| Unused Line of Credit
Related Party Transactions
Loans to related parties												74
Worldpay Holding, LLC \| Other Noninterest Income
Related Party Transactions
Equity Method Investment, Summarized Financial Information, Net Income (Loss)											2	1	47
Worldpay Holding, LLC \| Beyond Deconversion Period
Related Party Transactions
Revenue from Related Parties											$ 87	75	68
Vantiv, Inc
Related Party Transactions
Gain on sale of Worldpay, Inc. shares				116										$ 49
Amount Of Cash Flow Sales From 2017 To 2035				331										$ 140
TRA Obligations Settled Due Exercised Options Exercised												108	63
Potential Termination And Settlement Of Tra Cash Flows				394
Pretax Gain Recognized				$ 164
SLK Global
Related Party Transactions
Equity Method Investment, Ownership Percentage											49.00%
Dividend on Equity method investment in Vantiv Holding, LLC											$ 1
Service fee paid to Vantiv Holding, LLC											22	21	$ 21
Equity investments, carrying value											26	23
SLK Global \| Other Noninterest Income
Related Party Transactions
Revenue from Related Parties											3	2
CDC
Related Party Transactions
Loans to related parties											12	83
Related Party Deposit Liabilities											116	77
CDC \| Unfunded Commitment
Related Party Transactions
Due To Other Related Parties Current And Noncurrent											21	$ 80
Worldpay, Inc.
Related Party Transactions
Membership Units	10,252,826
Worldpay, Inc. \| Other Noninterest Income
Related Party Transactions
Recognized gain	$ 562
Fidelity National Information Services, Inc. and Worldpay, Inc
Related Party Transactions
Gain on sale of Worldpay, Inc. shares											345
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows											366
Potential Termination And Settlement Of Tra Cash Flows											$ 720