Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 1,382,442,000		$ 1,382,442,000		$ 1,382,442,000
Goodwill impairment	0	$ 0	0	$ 0
Net impairment (net recovery)	(32,000)	188,000	(864,000)	966,000
Amortization of other intangible assets	5,298,000	6,377,000	$ 16,753,000	18,528,000
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period, years			8 years 10 months 24 days
Other
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period, years			7 years 7 months 6 days
Core Deposits and Other
Finite-Lived Intangible Assets [Line Items]
Impairment of core deposits and other intangibles	$ 0	$ 0	$ 0	$ 0