Comprehensive Income - Summary of Changes in Components of Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 827,014	$ 763,784
Other comprehensive loss, net of tax	(31,100)	(13,088)
Balance at end of period	1,089,282	768,065
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	3,264	11,397
Other comprehensive loss, net of tax	(31,100)	(13,088)
Balance at end of period	(27,836)	(1,691)
Unrealized Gains (Losses) on Available for  Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	745	11,402
Other comprehensive loss, net of tax	(30,965)	(13,135)
Balance at end of period	(30,220)	(1,733)
Amortization of Gain on Debt Securities Reclassified to Held to Maturity
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	2,519
Other comprehensive loss, net of tax	(135)	0
Balance at end of period	2,384
Unrealized Gains (Losses) on Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		25
Other comprehensive loss, net of tax	$ 0	47
Balance at end of period		72
Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		(30)
Other comprehensive loss, net of tax		0
Balance at end of period		$ (30)