Derivative Financial Instruments - Narrative (Details)	3 Months Ended	6 Months Ended
Derivative Financial Instruments - Narrative (Details)	Mar. 31, 2022 USD ($)	Jun. 30, 2025 USD ($) derivativeInstrument	Dec. 31, 2024 USD ($) derivativeInstrument	Jun. 30, 2024 derivativeInstrument	Jun. 30, 2022 USD ($) derivativeInstrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) to be reclassified from accumulated other comprehensive income during the next 12 months		$ 2,200,000
Net derivative liability position, aggregate fair value		45,000
Interest Rate Swap Terminated
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) to be reclassified from accumulated other comprehensive income during the next 12 months		13,300,000
Interest Rate Swap And Collar
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) to be reclassified from accumulated other comprehensive income during the next 12 months		(15,500,000)
Mortgage banking derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 330,000,000.0	$ 295,000,000.0
Number of derivative instruments held \| derivativeInstrument		8	10
Not designated as hedging instrument \| Interest rate contract
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 0
Not designated as hedging instrument \| Interest rate contract, qualified borrowers
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		13,700,000,000	$ 13,300,000,000
Not designated as hedging instrument \| Interest rate lock commitments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		201,000,000.0	120,700,000
Not designated as hedging instrument \| Forward commitments to sell mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		467,900,000	377,500,000
Not designated as hedging instrument \| Commodity forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		2,100,000	5,200,000
Not designated as hedging instrument \| Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 117,500,000	$ 97,100,000
Not designated as hedging instrument \| Covered call options
Derivative Instruments, Gain (Loss) [Line Items]
Number of derivative instruments held \| derivativeInstrument		0	0	0
Interest rate derivatives designated as Cash Flow Hedges \| Designated as hedging instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 7,950,000,000
Interest rate derivatives designated as Cash Flow Hedges \| Designated as hedging instrument \| Interest Rate Swap Terminated
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 1,000,000,000				$ 500,000,000
Derivative term	5 years
Fair value of derivative contracts	$ 66,500,000
Number of derivative instruments held \| derivativeInstrument					1
Interest rate derivatives designated as Cash Flow Hedges \| Designated as hedging instrument \| Interest Rate Swap Terminated, Original Swap Maturing April 2024
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of derivative contracts					$ 10,700,000
Interest rate derivatives designated as Fair Value Hedges \| Designated as hedging instrument \| Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 143,100,000
Number of interest rate derivatives \| derivativeInstrument		13

WINTRUST FINANCIAL CORP 10-Q