Investment Securities

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Our available-for-sale investment securities were as follows:


	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
	(In thousands)
March 31, 2024
Corporate bonds	$	10,000	$	—	$	(333)	$	9,667

Agency bond securities	240,492		—		(41,965)		198,527
Agency mortgage-backed securities	2,292,157		—		(344,683)		1,947,474
Municipal bonds	29,309		—		(6,005)		23,304

Total investment securities	$	2,571,958	$	—	$	(392,986)	$	2,178,972

December 31, 2023
Corporate bonds	$	10,000	$	—	$	(374)	$	9,626


Agency bond securities	240,447		—		(40,217)		200,230
Agency mortgage-backed securities	2,337,411		—		(333,901)		2,003,510
Municipal bonds	29,408		—		(5,773)		23,635

Total investment securities	$	2,617,266	$	—	$	(380,265)	$	2,237,001

As of March 31, 2024 and December 31, 2023, the gross unrealized losses and fair values of available-for-sale investment securities that were in unrealized loss positions were as follows:


	Less than 12 months				12 months or more				Total fair value		Total unrealized loss
	Fair value		Unrealized loss		Fair value		Unrealized loss
	(In thousands)
March 31, 2024
Corporate bonds	$	—	$	—	$	9,667	$	(333)	$	9,667	$	(333)
Agency bond securities	—		—		198,527		(41,965)		198,527		(41,965)
Agency mortgage-backed securities	2,219		(1)		1,945,250		(344,682)		1,947,469		(344,683)
Municipal bonds	—		—		23,304		(6,005)		23,304		(6,005)

Total investment securities	$	2,219	$	(1)	$	2,176,748	$	(392,985)	$	2,178,967	$	(392,986)

December 31, 2023
Corporate bonds	$	—	$	—	$	9,626	$	(374)	$	9,626	$	(374)

Agency bond securities	—		—		200,230		(40,217)		200,230		(40,217)
Agency mortgage-backed securities	—		—		2,001,270		(333,901)		2,001,270		(333,901)
Municipal bonds	—		—		23,636		(5,773)		23,636		(5,773)

Total investment securities	$	—	$	—	$	2,234,762	$	(380,265)	$	2,234,762	$	(380,265)

Our investments generally consist of highly rated securities, substantially all of which are directly or indirectly backed by the U.S. federal government, as our investment policy restricts our investments to highly liquid, low credit risk assets. As such, we have not recorded any credit-related impairment losses during the three months ended March 31, 2024 or 2023 on our available-for-sale investment securities. Unrealized losses as of March 31, 2024 and December 31, 2023 are the result of increases in interest rates as our investment portfolio is comprised predominantly of fixed rate securities. All of the underlying securities within our investment portfolio were in an unrealized loss position as of March 31, 2024 and December 31, 2023 due to the timing of our investment purchases, as a significant portion of our investments were purchased prior to increases in interest rates by the Federal Reserve, and general volatility in market conditions.

We do not currently intend to sell our investments, and we have determined that it is more likely than not that we will not be required to sell our investments before recovery of their amortized cost bases, which may be at maturity.

Note 4—Investment Securities (continued)

As of March 31, 2024, the contractual maturities of our available-for-sale investment securities were as follows:


	Amortized cost		Fair value
	(In thousands)
Due in one year or less	$	60,691	$	60,117
Due after one year through five years	81,268		72,799
Due after five years through ten years	144,224		117,497
Due after ten years	54,309		41,202
Mortgage and asset-backed securities	2,231,466		1,887,357
Total investment securities	$	2,571,958	$	2,178,972

The expected payments on mortgage-backed and asset-backed securities may not coincide with their contractual maturities because the issuers have the right to call or prepay certain obligations.