Capital - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Oct. 31, 2021
Subsequent Event [Line Items]
Shareholders' equity	$ 1,554,376,000	$ 1,405,165,000	$ 1,314,274,000	$ 1,052,074,000
Increase (decrease) in equity	149,200,000
Net Income	152,302,000	142,572,000	157,063,000
Payments of dividends	55,489,000	52,602,000	50,814,000
Purchase of treasury stock	$ 35,792,000	$ 12,630,000	$ 14,965,000
Cash Dividends Declared per Common Share (in dollars per share)	$ 0.535	$ 0.515	$ 0.495
Borrowings	$ 0
Treasury stock reissued	2,881,000	$ 2,529,000	$ 2,211,000
Dividends, Common Stock, Cash	(55,489,000)	(52,602,000)	(50,814,000)
Treasury Stock, Value, Acquired, Cost Method	(36,452,000)	(12,717,000)	(15,083,000)
Total other comprehensive (loss) Income	37,914,000	9,242,000	25,936,000
Parent Company [Member]
Subsequent Event [Line Items]
Shareholders' equity	1,554,376,000	1,405,165,000
Net Income	152,302,000	142,572,000	157,063,000
Payments of dividends	55,489,000	52,602,000	50,814,000
Purchase of treasury stock	35,792,000	12,630,000	14,965,000
Payments to Acquire Businesses and Interest in Affiliates	$ (19,000)	$ (14,000)	$ (18,000)
2021 Share Repurchase Plan 2
Subsequent Event [Line Items]
Announcement of common stock repurchase program					$ 25,000,000.0
Stock repurchased (in shares)	5,247,990
Average price per share	$ 14.75