Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024
Investment Securities [Line Items]
Total debt securities, Amortized Cost		$ 1,096,232	$ 1,267,747
Gross Unrealized Gains		5,681	5,438
Gross Unrealized Losses		(87,719)	(125,562)
Securities available for sale		1,014,194	1,147,623
US States and Political Subdivisions Debt Securities [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		7,560	8,510
Gross Unrealized Gains		1	0
Gross Unrealized Losses		(590)	(983)
Securities available for sale		6,971	7,527
Corporate Securities [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		46,969	62,475
Gross Unrealized Gains		782	1,454
Gross Unrealized Losses		(1,220)	(2,436)
Securities available for sale		46,531	61,493
Obligations of U.S. Government-Sponsored Enterprises [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost	[1]	336,500
Securities available for sale		295,500
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		336,493	413,434
Gross Unrealized Gains		1,087	1,481
Gross Unrealized Losses		(42,057)	(64,331)
Securities available for sale		295,523	350,584
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		1,000	1,000
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(16)	(54)
Securities available for sale		984	946
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		701,572	779,232
Gross Unrealized Gains		3,788	2,489
Gross Unrealized Losses		(43,671)	(57,546)
Securities available for sale		661,689	724,175
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member]
Investment Securities [Line Items]
Total debt securities, Amortized Cost		2,638	3,096
Gross Unrealized Gains		23	14
Gross Unrealized Losses		(165)	(212)
Securities available for sale		$ 2,496	$ 2,898

[1] Mortgage-Backed Securities include an amortized cost of $704.2 million and a fair value of $664.2 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $336.5 million and a fair value of $295.5 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.