Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Investment Securities [Line Items]
Amortized Cost	$ 1,045,579	$ 805,515
Gross Unrealized Gains	9,515	25,708
Gross Unrealized Losses	(13,714)	0
Securities available for sale	1,041,380	831,223
Estimated Fair Value, Less Than 12 Months	1,032,863	3,755
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(22,142)	(10)
Estimated Fair Value, 12 Months or More	0	0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0	0
Securities Continuous Unrealized Loss Position Fair Value	1,032,863	3,755
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	(22,142)	(10)
US States and Political Subdivisions Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	9,538	11,154
Gross Unrealized Gains	89	243
Gross Unrealized Losses	(103)	0
Securities available for sale	9,524	11,397
Corporate Securities [Member]
Investment Securities [Line Items]
Amortized Cost	32,088	22,941
Gross Unrealized Gains	973	1,444
Gross Unrealized Losses	(112)	0
Securities available for sale	32,949	24,385
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member]
Investment Securities [Line Items]
Amortized Cost	632,687	481,109
Gross Unrealized Gains	6,308	14,924
Gross Unrealized Losses	(9,021)	0
Securities available for sale	629,974	496,033
Estimated Fair Value, Less Than 12 Months	658,965	3,755
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(14,779)	(10)
Estimated Fair Value, 12 Months or More	0	0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0	0
Securities Continuous Unrealized Loss Position Fair Value	658,965	3,755
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	(14,779)	(10)
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Investment Securities [Line Items]
Amortized Cost	1,000	100,996
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(19)	0
Securities available for sale	981	100,998
Estimated Fair Value, Less Than 12 Months	22,261
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(644)
Estimated Fair Value, 12 Months or More	0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0
Securities Continuous Unrealized Loss Position Fair Value	22,261
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	(644)
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	365,024	182,823
Gross Unrealized Gains	1,725	8,357
Gross Unrealized Losses	(4,459)	0
Securities available for sale	362,290	191,180
Estimated Fair Value, Less Than 12 Months	320,414
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(6,398)
Estimated Fair Value, 12 Months or More	0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0
Securities Continuous Unrealized Loss Position Fair Value	320,414
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	(6,398)
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member]
Investment Securities [Line Items]
Amortized Cost	5,242	6,492
Gross Unrealized Gains	420	738
Gross Unrealized Losses	0	0
Securities available for sale	$ 5,662	$ 7,230