Accumulated Other Comprehensive Loss - Amounts Reclassified Out of Each Component of Accumulated Other Comprehensive Loss (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains (losses) on available-for-sale securities	$ 0	$ 0
Other operating expenses	(3,198,000)	(2,172,000)
Income tax expense	(2,528,000)	(1,551,000)
Net Income	12,888,000	8,466,000
Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income	0	(55,000)
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	0
Income tax expense	0	0
Net Income	0	0
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	(69,000)
Income tax expense	0	14,000
Net Income	$ (0)	$ (55,000)