Parent-only Financial Information - Statement of Cash Flows (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 86,173,000	$ 92,049,000	$ 57,603,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	1,980,000	1,025,000	1,048,000
Gain on securities transactions	(210,000)	(2,025,000)	(370,000)
Change in fair value of equity securities	401,000	1,792,000	(767,000)
Deferred tax expense	12,769,000	17,709,000	9,738,000
(Increase) in other assets	(9,884,000)	(22,159,000)	(75,127,000)
Increase in accrued expenses and other liabilities	24,998,000	1,926,000	32,891,000
Net cash provided by operating activities	142,158,000	98,704,000	49,044,000
Cash flows from investing activities:
Proceeds from sales of equity securities	0	1,390,000	0
Proceeds from paydown/maturities/calls of debt securities available for sale	281,959,000	368,249,000	247,908,000
Purchases of equity securities	0	(91,000)	0
Repayment of loan receivable from Columbia Bank	0	0	35,613,000
Net cash acquired in acquisitions	140,769,000	20,417,000	155,248,000
Net cash (used in) provided by investing activities	(614,725,000)	(443,605,000)	257,645,000
Cash flows from financing activities:
Payment of subordinated debt	0	0	(16,600,000)
Proceeds from term note	0	29,841,000	0
Purchase of treasury stock	(93,996,000)	(107,774,000)	(108,166,000)
Restricted stock forfeitures	0	0	(24,000)
Repurchase of shares for taxes	(4,614,000)	(357,000)	(174,000)
Net cash provided by (used in) financing activities	580,832,000	(7,093,000)	40,721,000
Net increase (decrease) in cash and cash equivalents	108,265,000	(351,994,000)	347,410,000
Cash and cash equivalents at beginning of year	70,963,000	422,957,000	75,547,000
Cash and cash equivalents at end of year	179,228,000	70,963,000	422,957,000
Acquisition:
Net cash and cash equivalents acquired in acquisition	140,769,000	20,417,000	155,248,000
Parent Company
Cash flows from operating activities:
Net income	86,173,000	92,049,000	57,603,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	73,000	21,000	(278,000)
Gain on securities transactions	0	(383,000)	(2,000)
Change in fair value of equity securities	15,000	35,000	115,000
Deferred tax expense	2,463,000	1,830,000	1,411,000
(Increase) in other assets	(642,000)	(7,721,000)	(2,675,000)
Increase in accrued expenses and other liabilities	(997,000)	691,000	(647,000)
Equity in undistributed (earnings)of subsidiaries	(9,132,000)	(27,652,000)	(8,027,000)
Net cash provided by operating activities	77,953,000	58,870,000	47,500,000
Cash flows from investing activities:
Proceeds from sales of equity securities	0	1,390,000	0
Proceeds from paydown/maturities/calls of debt securities available for sale	0	0	1,498,000
Purchases of equity securities	0	(91,000)	0
Repayment of loan receivable from Columbia Bank	1,675,000	1,599,000	1,521,000
Net cash acquired in acquisitions	31,000	0	0
Net cash (used in) provided by investing activities	1,706,000	2,898,000	3,019,000
Cash flows from financing activities:
Payment of subordinated debt	0	0	(16,600,000)
Proceeds from term note	0	29,841,000	0
Purchase of treasury stock	(93,996,000)	(107,774,000)	(108,166,000)
Exercise of stock options	325,000	(25,000)	0
Issuance of common stock allocated to restricted stock award grants	2,624,000	0	0
Restricted stock forfeitures	(1,451,000)	(1,234,000)	(199,000)
Repurchase of shares for taxes	(4,614,000)	(357,000)	(181,000)
Issuance of treasury stock allocated to restricted stock award grants	0	896,000	481,000
Net cash provided by (used in) financing activities	(97,112,000)	(78,653,000)	(124,665,000)
Net increase (decrease) in cash and cash equivalents	(17,453,000)	(16,885,000)	(74,146,000)
Cash and cash equivalents at beginning of year	77,338,000	94,223,000	168,369,000
Cash and cash equivalents at end of year	59,885,000	77,338,000	94,223,000
Acquisition:
Net cash and cash equivalents acquired in acquisition	$ 31,000	$ 0	$ 0