Condensed Financial Information - Parent Company Only - Condensed Statements of Cash Flows (Detail) - USD ($)			12 Months Ended
		Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows from Operating Activities
Net Income			$ 95,041,000	$ 57,518,000	$ 70,672,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Gain on sale of equity securities			(9,000)	(1,213,000)	0
Benefit for credit losses	[1]		(10,896,000)	27,222,000	2,130,000
Long-term debt extinguishment costs		$ 831,000	831,000	0	0
Change in fair value of equity securities			285,000	552,000	(496,000)
Excess tax (deficiencies) benefits			(89,000)	(132,000)	189,000
Increase in other assets			36,589,000	(53,982,000)	(13,246,000)
Increase in other liabilities			(37,389,000)	50,434,000	15,092,000
Net Cash Provided by Operating Activities			95,103,000	84,991,000	87,131,000
Cash Flows from Investing Activities
Purchase of equity securities			(2,959,000)	(2,772,000)	(1,343,000)
Proceeds from repayments and maturities of held to maturity securities			66,709,000	38,941,000	31,457,000
Proceeds from sales of equity securities			0	4,148,000	1,287,000
Net cash received from business acquisition			0	0	13,454,000
Net Cash Used in Investing Activities:			(615,290,000)	(928,022,000)	(303,977,000)
Cash Flows from Financing Activities
Cash dividends paid on common stock			(27,119,000)	(25,457,000)	(24,919,000)
Proceeds from issuance of subordinated debt, net			147,738,000	0	0
Redemption of subordinated debentures, net			(88,330,000)	0	0
Purchase of treasury stock			0	(1,452,000)	0
Retirement of restricted stock			(651,000)	(501,000)	(715,000)
Exercise of stock options			19,000	0	313,000
Net Cash Provided by Financing Activities:			478,627,000	830,750,000	290,618,000
Net (decrease) increase in cash and cash equivalents			(41,560,000)	(12,281,000)	73,772,000
Cash and cash equivalents, beginning of year			270,090,000	282,371,000	208,599,000
Cash and Cash Equivalents, End of Year			228,530,000	270,090,000	282,371,000
Parent Company
Cash Flows from Operating Activities
Net Income			95,041,000	57,518,000	70,672,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Gain on sale of equity securities			0	(149,000)	0
Amortization of subordinated debt costs			547,000	37,000	36,000
Benefit for credit losses			0	(12,000)	0
Long-term debt extinguishment costs			831,000	0	0
Change in fair value of equity securities			0	786,000	(197,000)
Excess tax (deficiencies) benefits			(89,000)	(132,000)	189,000
Increase in other assets			(1,443,000)	(1,462,000)	(1,873,000)
Increase in other liabilities			149,000	25,000	121,000
Equity in undistributed income of subsidiaries			(49,831,000)	(32,915,000)	(38,160,000)
Net Cash Provided by Operating Activities			45,205,000	23,696,000	30,788,000
Cash Flows from Investing Activities
Purchase of equity securities			0	(49,000)	(82,000)
Proceeds from repayments and maturities of held to maturity securities			0	1,000,000	0
Proceeds from sales of equity securities			0	1,148,000	1,287,000
Net cash received from business acquisition			0	0	24,000
Contribution to subsidiary			(65,000,000)	0	0
Net Cash Used in Investing Activities:			(65,000,000)	2,099,000	1,229,000
Cash Flows from Financing Activities
Cash dividends paid on common stock			(27,119,000)	(25,457,000)	(24,919,000)
Proceeds from issuance of common stock, net			0	0	0
Proceeds from issuance of subordinated debt, net			147,738,000	0	0
Redemption of subordinated debentures, net			(88,330,000)	0	0
Purchase of treasury stock			0	(1,452,000)	0
Retirement of restricted stock			(651,000)	(501,000)	(715,000)
Exercise of stock options			19,000	0	313,000
Net Cash Provided by Financing Activities:			31,657,000	(27,410,000)	(25,321,000)
Net (decrease) increase in cash and cash equivalents			11,862,000	(1,615,000)	6,696,000
Cash and cash equivalents, beginning of year			28,366,000	29,981,000	23,285,000
Cash and Cash Equivalents, End of Year			$ 40,228,000	$ 28,366,000	$ 29,981,000

[1] The Company adopted ASU 2016-13 as of December 31, 2020. Prior year periods have not been restated.