Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)	$ (44)	$ (301)	$ 995
Unrealized gains, net of tax	2,441	0	0
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)	(44)	(301)	995
Reclassifications, net of tax	(44)	(301)
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	7	7	7
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	$ 2,404	$ (294)	$ 1,002