Condensed Financial Information - Parent Company Only - Schedule of Condensed Cash Flow Statement (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income		$ 91,801,000	$ 46,916,000	$ 65,719,000
Adjustments to reconcile net income to net cash provided by operating activities:
Bank owned life insurance income	[1]	(3,981,000)	(2,940,000)	(3,179,000)
Depreciation of premises and equipment		4,662,000	4,780,000	5,277,000
Stock-based compensation		3,698,000	1,480,000	2,348,000
Contributions to pension and other postretirement benefit plans		(265,000)	(270,000)	(266,000)
(Increase) decrease in other assets		(3,131,000)	(2,835,000)	(2,332,000)
Increase in accrued interest payable and other liabilities		2,195,000	8,608,000	1,409,000
Net cash provided by operating activities		102,337,000	51,179,000	73,148,000
Cash flows from investing activities:
Net cash used in investing activities		(126,779,000)	(867,392,000)	(343,369,000)
Cash flows from financing activities:
Proceeds from issuance of subordinated notes		0	100,000,000	0
Purchases of treasury stock		(295,000)	(4,382,000)	(2,045,000)
Stock issued under dividend reinvestment and employee stock purchase plans		2,384,000	2,369,000	2,233,000
Proceeds from exercise of stock options		2,058,000	384,000	1,203,000
Cash dividends paid		(23,575,000)	(17,536,000)	(23,435,000)
Net cash provided by financing activities		694,734,000	910,943,000	285,929,000
Cash and cash equivalents at beginning of year		219,858,000	125,128,000	109,420,000
Cash and cash equivalents at end of year		890,150,000	219,858,000	125,128,000
Cash paid during the year for:
Interest		21,824,000	29,233,000	44,479,000
Income tax, net of refunds received		26,589,000	17,316,000	17,171,000
Parent Company [Member]
Cash flows from operating activities:
Net income		91,801,000	46,916,000	65,719,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries		(42,211,000)	(43,426,000)	(40,810,000)
Bank owned life insurance income		(111,000)	(108,000)	(331,000)
Depreciation of premises and equipment		304,000	320,000	328,000
Stock-based compensation		3,698,000	1,480,000	2,348,000
Contributions to pension and other postretirement benefit plans		(265,000)	(270,000)	(266,000)
(Increase) decrease in other assets		(5,654,000)	2,321,000	554,000
Increase in accrued interest payable and other liabilities		2,510,000	(4,631,000)	(1,319,000)
Net cash provided by operating activities		50,072,000	2,602,000	26,223,000
Cash flows from investing activities:
Other, net		(68,000)	(32,000)	(371,000)
Net cash used in investing activities		(68,000)	(32,000)	(371,000)
Cash flows from financing activities:
Proceeds from issuance of subordinated notes		0	98,448,000	0
Repayments of Subordinated Debt		(85,000,000)	(10,000,000)	0
Purchases of treasury stock		(650,000)	(4,452,000)	(2,045,000)
Stock issued under dividend reinvestment and employee stock purchase plans		2,384,000	2,369,000	2,233,000
Proceeds from exercise of stock options		2,058,000	384,000	1,203,000
Cash dividends paid		(23,575,000)	(17,536,000)	(23,435,000)
Net cash provided by financing activities		(104,783,000)	69,213,000	(22,044,000)
Net increase in cash and cash equivalents		(54,779,000)	71,783,000	3,808,000
Cash and cash equivalents at beginning of year		154,633,000	82,850,000	79,042,000
Cash and cash equivalents at end of year		99,854,000	154,633,000	82,850,000
Cash paid during the year for:
Interest		6,929,000	5,121,000	4,800,000
Income tax, net of refunds received		$ 18,130,000	$ 16,172,000	$ 16,460,000

[1] Net interest income as well as many other revenues for financial assets and liabilities including loans, leases, securities, and derivatives are excluded from the scope of FASB ASC 606 "Revenue from Contracts with Customers" (FASB ASC 606). Noninterest income streams that are out of scope of FASB ASC 606 include bank owned life insurance income, sales of investment securities and mortgage banking activities.