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Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($)			3 Months Ended
	Feb. 15, 2022	Aug. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Goodwill [Line Items]
Acquisitions and adjustments			$ 960,163,000	$ 0
Goodwill impairment		$ 0
Impairment charges			0	0
Amortization of other intangible assets			$ 4,811,000	$ 3,075,000
Core Deposits and Other Intangible Assets \| Minimum
Goodwill [Line Items]
Estimated useful lives			5 years
Core Deposits and Other Intangible Assets \| Maximum
Goodwill [Line Items]
Estimated useful lives			15 years
Core deposit
Goodwill [Line Items]
Estimated fair value of intangible assets acquired			$ 77,900,000
Customer trust relationships
Goodwill [Line Items]
Estimated fair value of intangible assets acquired			39,700,000
First Midwest
Goodwill [Line Items]
Acquisitions and adjustments			$ 960,200,000
First Midwest \| Core deposit
Goodwill [Line Items]
Estimated useful lives	10 years
First Midwest \| Customer trust relationships
Goodwill [Line Items]
Estimated useful lives	13 years