Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of Each Component of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other operating expenses	$ (3,388)	$ (2,828)	$ (9,792)	$ (7,450)
Income tax expense	(1,860)	(2,206)	(6,068)	(5,180)
Net Income	10,387	11,112	33,309	27,279
Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income	0	(50)	0	(156)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains (losses) on available-for-sale securities	0	4	0	10
Income tax expense	0	0	0	(2)
Net Income	0	4	0	8
Accumulated Defined Benefit Plans Adjustment, Actuarial gains/(Losses) [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other operating expenses	0	(69)	0	(208)
Income tax expense	0	15	0	44
Net Income	$ (0)	$ (54)	$ 0	$ (164)