Summary of unrealized losses for available-for-sale securities

The tables below summarize the available-for-sale securities with unrealized losses as of the dates shown, along with the length of the impairment period:


	March 31, 2023
	Less than 12 months				12 months or more				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
U.S. Treasury securities	$	72,153	$	(1,994)	$	—	$	—	$	72,153	$	(1,994)
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		43,304		(2,112)		175,914		(31,964)		219,218		(34,076)
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		25,905		(1,745)		372,230		(63,880)		398,135		(65,625)
Municipal securities		154		(1)		—		—		154		(1)
Corporate debt		1,892		(108)		—		—		1,892		(108)
Total	$	143,408	$	(5,960)	$	548,144	$	(95,844)	$	691,552	$	(101,804)


	December 31, 2022
	Less than 12 months				12 months or more				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
U.S. Treasury securities	$	71,388	$	(2,643)	$	—	$	—	$	71,388	$	(2,643)
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		83,748		(6,686)		141,272		(31,123)		225,020		(37,809)
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		196,449		(22,809)		209,477		(50,131)		405,926		(72,940)
Municipal securities		153		(2)		—		—		153		(2)
Corporate debt		1,920		(80)		—		—		1,920		(80)
Total	$	353,658	$	(32,220)	$	350,749	$	(81,254)	$	704,407	$	(113,474)

Schedule of credit quality indicators, by fair value, of available-for-sale securities

The tables below summarize the credit quality indicators, by fair value, of available-for-sale securities as of the dates shown:


	March 31, 2023
	AAA		Not rated		Total
U.S. Treasury securities	$	72,154	$	—	$	72,154
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		222,209		—		222,209
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		398,282		—		398,282
Municipal securities		—		154		154
Corporate debt		—		1,892		1,892
Other securities		—		794		794
Total investment securities available-for-sale	$	692,645	$	2,840	$	695,485


	December 31, 2022
	AAA		Not rated		Total
U.S. Treasury securities	$	71,388	$	—	$	71,388
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		226,131		—		226,131
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		405,926		—		405,926
Municipal securities		—		153		153
Corporate debt		—		1,920		1,920
Other securities		—		771		771
Total investment securities available-for-sale	$	703,445	$	2,844	$	706,289

Summary of unrealized losses for held-to-maturity securities

The held-to-maturity portfolio included 111 securities which were in an unrealized loss position as of March 31, 2023 compared to 129 securities at December 31, 2022. The tables below summarize the held-to-maturity securities with unrealized losses as of the dates shown, along with the length of the impairment period:


	March 31, 2023
	Less than 12 months				12 months or more				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
U.S. Treasury securities	$	48,141	$	(976)	$	—	$	—	$	48,141	$	(976)
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		48,855		(1,481)		195,980		(35,798)		244,835		(37,279)
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		23,337		(684)		185,348		(44,283)		208,685		(44,967)
Total	$	120,333	$	(3,141)	$	381,328	$	(80,081)	$	501,661	$	(83,222)


	December 31, 2022
	Less than 12 months				12 months or more				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
U.S. Treasury securities	$	47,629	$	(1,416)	$	—	$	—	$	47,629	$	(1,416)
Mortgage-backed securities:
Residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises		83,323		(3,804)		182,159		(37,358)		265,482		(41,162)
Other residential MBS issued or guaranteed by U.S. Government agencies or sponsored enterprises		34,704		(1,145)		178,776		(48,043)		213,480		(49,188)
Total	$	165,656	$	(6,365)	$	360,935	$	(85,401)	$	526,591	$	(91,766)