Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reconciliations of total equity
Beginning Balance	$ 1,200,538	$ 1,214,522	$ 1,169,934	$ 1,216,490
Issuance of common stock under incentive compensation plan	22	101	104	966
Stock-based and deferred compensation	2,145	2,357	1,090	(283)
Net income	11,341	9,521	31,052	23,414
Other comprehensive income (loss)	36,369	(25,634)	56,919	(31,298)
Cash dividends paid:
Common stock	(8,702)	(8,431)	(17,386)	(16,853)
Ending Balance	1,241,713	1,192,436	1,241,713	1,192,436
Common Stock [Member]
Reconciliations of total equity
Beginning Balance	27,253	27,125	27,156	27,006
Issuance of common stock under incentive compensation plan		2	2	23
Stock-based and deferred compensation	38	15	133	113
Cash dividends paid:
Ending Balance	27,291	27,142	27,291	27,142
Additional Paid-in Capital [Member]
Reconciliations of total equity
Beginning Balance	254,366	248,337	253,779	247,032
Issuance of common stock under incentive compensation plan	22	99	102	943
Stock-based and deferred compensation	2,187	2,509	2,694	2,970
Cash dividends paid:
Ending Balance	256,575	250,945	256,575	250,945
Common Treasury Stock [Member]
Reconciliations of total equity
Beginning Balance	(189,706)	(187,611)	(188,049)	(184,412)
Stock-based and deferred compensation	(80)	(167)	(1,737)	(3,366)
Cash dividends paid:
Ending Balance	(189,786)	(187,778)	(189,786)	(187,778)
Accumulated Other Comprehensive Income (Loss) [Member]
Reconciliations of total equity
Beginning Balance	(176,288)	(136,266)	(196,838)	(130,602)
Other comprehensive income (loss)	36,369	(25,634)	56,919	(31,298)
Cash dividends paid:
Ending Balance	(139,919)	(161,900)	(139,919)	(161,900)
Retained Earnings [Member]
Reconciliations of total equity
Beginning Balance	1,284,913	1,262,937	1,273,886	1,257,466
Net income	11,341	9,521	31,052	23,414
Cash dividends paid:
Common stock	(8,702)	(8,431)	(17,386)	(16,853)
Ending Balance	$ 1,287,552	$ 1,264,027	$ 1,287,552	$ 1,264,027