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Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (loss) Pre-Tax and After-Tax (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
After-tax
Other comprehensive income (loss)	$ (27,531)	$ (29,656)	$ (42,910)	$ (1,827)	$ 7,996	$ (16,910)	$ (100,097)	$ (10,741)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent
Pre-tax
Unrealized holding gains (losses) arising during the period	(36,715)			(1,635)			(134,148)	(13,796)
Less: Reclassification adjustments for (gains) losses realized in net income (loss)	210			(690)			1,423	(243)
Other comprehensive income (loss)	(36,505)			(2,325)			(132,725)	(14,039)
Tax
Unrealized holding gains (losses) arising during the period	(9,026)			(334)			(32,978)	(3,241)
Less: Reclassification adjustments for (gains) losses realized in net income (loss)	52			(164)			350	(57)
Other comprehensive income (loss)	(8,974)			(498)			(32,628)	(3,298)
After-tax
Unrealized holding gains (losses) arising during the period	(27,689)			(1,301)			(101,170)	(10,555)
Less: Reclassification adjustments for (gains) losses realized in net income (loss)	158			(526)			1,073	(186)
Other comprehensive income (loss)	$ (27,531)			$ (1,827)			$ (100,097)	$ (10,741)