Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reconciliations of total equity
Beginning Balance	$ 1,192,436	$ 1,215,097	$ 1,216,490	$ 1,166,065
Issuance of common stock under incentive compensation plan	57	470	1,023	2,386
Stock-based and deferred compensation	1,524	1,750	1,241	1,215
Net Income	23,606	12,571	47,020	41,397
Other comprehensive income (loss)	10,178	(18,955)	(21,120)	16,187
Cash dividends paid:
Common stock	(8,436)	(8,162)	(25,289)	(24,479)
Ending Balance	1,219,365	1,202,771	1,219,365	1,202,771
Common Stock [Member]
Reconciliations of total equity
Beginning Balance	27,142	26,978	27,006	26,841
Issuance of common stock under incentive compensation plan	1	11	24	44
Stock-based and deferred compensation	6		119	104
Cash dividends paid:
Ending Balance	27,149	26,989	27,149	26,989
Additional Paid-in Capital [Member]
Reconciliations of total equity
Beginning Balance	250,945	242,215	247,032	237,202
Issuance of common stock under incentive compensation plan	56	459	999	2,342
Stock-based and deferred compensation	1,674	1,757	4,644	4,887
Cash dividends paid:
Ending Balance	252,675	244,431	252,675	244,431
Common Treasury Stock [Member]
Reconciliations of total equity
Beginning Balance	(187,778)	(184,365)	(184,412)	(180,596)
Stock-based and deferred compensation	(156)	(7)	(3,522)	(3,776)
Cash dividends paid:
Ending Balance	(187,934)	(184,372)	(187,934)	(184,372)
Accumulated Other Comprehensive Income (Loss) [Member]
Reconciliations of total equity
Beginning Balance	(161,900)	(132,370)	(130,602)	(167,512)
Other comprehensive income (loss)	10,178	(18,955)	(21,120)	16,187
Cash dividends paid:
Ending Balance	(151,722)	(151,325)	(151,722)	(151,325)
Retained Earnings [Member]
Reconciliations of total equity
Beginning Balance	1,264,027	1,262,639	1,257,466	1,250,130
Net Income	23,606	12,571	47,020	41,397
Cash dividends paid:
Common stock	(8,436)	(8,162)	(25,289)	(24,479)
Ending Balance	$ 1,279,197	$ 1,267,048	$ 1,279,197	$ 1,267,048