New Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unfunded commitments, allowance for credit loss		$ 22,400	$ 22,400
Undivided profits		1,093,270	901,006
Unrealized holding gains (losses) arising during the period on available-for-sale securities		(91,226)	107,382	$ 76,109
Right-of-use lease assets		48,855	31,348
Lease liability included in other liabilities		$ 49,321	$ 31,433
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans					$ 151,400
Unfunded commitments, allowance for credit loss					24,000
Debt securities, allowance for credit loss					742
Undivided profits					$ 128,100
Accounting Standards Update 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fair value of HTM municipal bonds	$ 216,400
Unrealized holding gains (losses) arising during the period on available-for-sale securities	$ 2,500
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use lease assets						$ 32,800
Lease liability included in other liabilities						$ 32,800