Debt Securities Available for Sale (Tables)

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Debt Securities, Available-for-Sale

Debt securities available for sale at March 31, 2024 and December 31, 2023 are summarized as follows:

	March 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Fair Value
	(In thousands)
U.S. government and agency obligations	$	239,128	$	225	$	(2,319)	$	237,034
Mortgage-backed securities and collateralized mortgage obligations	1,018,854		1		(149,638)		869,217
Municipal obligations	2,768		—		(60)		2,708
Corporate debt securities	92,548		—		(14,067)		78,481
	$	1,353,298	$	226	$	(166,084)	$	1,187,440

	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Fair Value
			(In thousands)
U.S. government and agency obligations	$	146,387	$	924	$	(1,810)	$	145,501
Mortgage-backed securities and collateralized mortgage obligations	1,009,508		20		(141,943)		867,585
Municipal obligations	2,770		—		(68)		2,702
Corporate debt securities	92,565		2		(14,798)		77,769
	$	1,251,230	$	946	$	(158,619)	$	1,093,557

Schedule of Securities by Contractual Maturity

The amortized cost and fair value of debt securities available for sale at March 31, 2024, by contractual final maturity, is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer.

	March 31, 2024
	Amortized Cost		Fair Value
	(In thousands)
One year or less	$	65,637	$	65,638
More than one year to five years	200,010		196,755
More than five years to ten years	68,797		55,830
	$	334,444	$	318,223
Mortgage-backed securities and collateralized mortgage obligations	1,018,854		869,217
	$	1,353,298	$	1,187,440

The amortized cost and fair value of debt securities held to maturity at March 31, 2024, by contractual final maturity, is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer.

	March 31, 2024
	Amortized Cost		Fair Value
	(In thousands)
More than one year to five years	$	29,875	$	27,610
More than five years to ten years	9,996		8,483
More than ten years	10,000		7,714
	49,871		43,807
Mortgage-backed securities and collateralized mortgage obligations	348,480		308,184
	$	398,351	$	351,991

Debt securities, available-for-sale, unrealized loss position, fair value

The following tables summarize the fair value and gross unrealized losses of those securities that reported an unrealized loss at March 31, 2024 and December 31, 2023 and if the unrealized loss position was continuous for the twelve months prior to those respective dates:

	March 31, 2024
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized (Losses)		Fair Value		Gross Unrealized (Losses)		Fair Value		Gross Unrealized (Losses)
	(In thousands)
U.S. government and agency obligations	$	102,990	$	(440)	$	25,704	$	(1,879)	$	128,694	$	(2,319)
Mortgage-backed securities and collateralized mortgage obligations	28,787		(129)		840,015		(149,509)		868,802		(149,638)
Municipal obligations	—		—		2,708		(60)		2,708		(60)
Corporate debt securities	—		—		78,481		(14,067)		78,481		(14,067)
	$	131,777	$	(569)	$	946,908	$	(165,515)	$	1,078,685	$	(166,084)

6.    Debt Securities Available for Sale (continued)

	December 31, 2023
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized (Losses)		Fair Value		Gross Unrealized (Losses)		Fair Value		Gross Unrealized (Losses)
	(In thousands)
U.S. government and agency obligations	$	—	$	—	$	21,344	$	(1,810)	$	21,344	$	(1,810)
Mortgage-backed securities and collateralized mortgage obligations	54		(4)		863,026		(141,939)		863,080		(141,943)
Municipal obligations	—		—		2,702		(68)		2,702		(68)
Corporate debt securities	—		—		75,765		(14,798)		75,765		(14,798)
	$	54	$	(4)	$	962,837	$	(158,615)	$	962,891	$	(158,619)