Acquisition and Divestiture Activity - Additional Information (Details) $ in Thousands			3 Months Ended		8 Months Ended	9 Months Ended
	Feb. 15, 2022 USD ($) agreement shares	May 30, 2021 shares	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Number of deposit agreements (in agreements) | agreement	2
Increase in goodwill			$ 11,065	$ 0		$ 965,605	$ 0
Purchase price of loans at acquisition	$ 1,400,000					1,390,273
Par value of acquired loans at acquisition	1,500,000					1,488,365
Allowance for credit losses at acquisition	$ 89,100					89,089
Accumulated benefit obligation			49,700		$ 49,700	49,700
Plan assets			67,100		67,100	67,100
Allowance for credit losses			302,254	$ 107,868	302,254	302,254	$ 107,868	$ 288,003	$ 107,341	$ 109,444	$ 131,388
Premium to be received on account balance transferred			95,000		95,000	95,000
Series A Preferred Stock
Business Acquisition [Line Items]
Shares issued for acquisition (in shares) | shares	108,000
Series C Preferred Stock
Business Acquisition [Line Items]
Shares issued for acquisition (in shares) | shares	122,500
Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series A
Business Acquisition [Line Items]
Shares issued for acquisition (in shares) | shares	4,320,000
Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series C
Business Acquisition [Line Items]
Shares issued for acquisition (in shares) | shares	4,900,000
First Midwest
Business Acquisition [Line Items]
Shares exchange ratio		1.1336
Number of shares to be received upon conversion (in shares) | shares		1
Increase in goodwill					5,400
Other intangible assets	$ 117,584
Transaction costs, expensed						100,600
Transaction costs			22,700			100,600
Allowance for credit losses			96,300		96,300	96,300
First Midwest | Unfunded Loan Commitment
Business Acquisition [Line Items]
Allowance for credit losses			$ 11,000		$ 11,000	$ 11,000
First Midwest | Core deposit
Business Acquisition [Line Items]
Other intangible assets	$ 77,900
Estimated useful lives	10 years
First Midwest | Customer trust relationships
Business Acquisition [Line Items]
Other intangible assets	$ 39,700
Estimated useful lives	13 years
First Midwest | Series A Preferred Stock
Business Acquisition [Line Items]
Dividend rate		7.00%
First Midwest | Series C Preferred Stock
Business Acquisition [Line Items]
Dividend rate		7.00%