The following tables summarize the amortized cost and fair value of available-for-sale securities by major type:


	At June 30, 2023
(In thousands)	Amortized Cost (1)		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury notes	$	407,555	$	—	$	(23,488)	$	384,067
Government agency debentures	302,115		—		(41,014)		261,101
Municipal bonds and notes	1,678,826		5		(74,681)		1,604,150
Agency CMO	58,529		—		(5,169)		53,360
Agency MBS	2,476,218		9		(291,320)		2,184,907
Agency CMBS	2,041,431		44		(306,553)		1,734,922
CMBS	907,602		—		(31,483)		876,119

Corporate debt	712,726		—		(103,967)		608,759
Private label MBS	47,485		—		(4,435)		43,050
Other	9,817		—		(911)		8,906
Total available-for-sale securities	$	8,642,304	$	58	$	(883,021)	$	7,759,341

	At December 31, 2022
(In thousands)	Amortized Cost (1)		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury notes	$	755,968	$	—	$	(38,928)	$	717,040
Government agency debentures	302,018		—		(43,644)		258,374
Municipal bonds and notes	1,719,110		5		(85,913)		1,633,202
Agency CMO	64,984		—		(5,019)		59,965
Agency MBS	2,461,337		26		(303,339)		2,158,024
Agency CMBS	1,664,600		—		(258,114)		1,406,486
CMBS	929,588		—		(32,948)		896,640
CLO	2,108		—		(1)		2,107
Corporate debt	795,999		—		(91,587)		704,412
Private label MBS	48,895		—		(4,646)		44,249
Other	12,548		—		(350)		12,198
Total available-for-sale securities	$	8,757,155	$	31	$	(864,489)	$	7,892,697

(1)Accrued interest receivable on available-for-sale securities of $37.1 million and $36.9 million at June 30, 2023, and December 31, 2022, respectively, is excluded from amortized cost and is included in Accrued interest receivable and other assets on the accompanying Condensed Consolidated Balance Sheets.


	At June 30, 2023
	Less Than 12 Months				12 Months or More				Total
(Dollars in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Number of Holdings	Fair Value		Unrealized Losses
U.S. Treasury notes	$	—	$	—	$	384,067	$	(23,488)	14	$	384,067	$	(23,488)
Government agency debentures	32,481		(2,376)		228,620		(38,638)		19	261,101		(41,014)
Municipal bonds and notes	30,722		(506)		1,554,918		(74,175)		420	1,585,640		(74,681)
Agency CMO	7,018		(349)		46,342		(4,820)		37	53,360		(5,169)
Agency MBS	197,989		(4,220)		1,986,029		(287,100)		465	2,184,018		(291,320)
Agency CMBS	345,784		(10,832)		1,347,550		(295,721)		142	1,693,334		(306,553)
CMBS	48,536		(1,439)		827,583		(30,044)		51	876,119		(31,483)

Corporate debt	8,805		(1,297)		599,954		(102,670)		92	608,759		(103,967)
Private label MBS	11,880		(1,153)		31,170		(3,282)		3	43,050		(4,435)
Other	4,789		(211)		4,117		(700)		2	8,906		(911)
Total	$	688,004	$	(22,383)	$	7,010,350	$	(860,638)	1,245	$	7,698,354	$	(883,021)


	At December 31, 2022
	Less Than Twelve Months				Twelve Months or Longer				Total
(Dollars in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Number of Holdings	Fair Value		Unrealized Losses
U.S. Treasury notes	$	337,563	$	(19,167)	$	379,477	$	(19,761)	23	$	717,040	$	(38,928)
Government agency debentures	258,374		(43,644)		—		—		19	258,374		(43,644)
Municipal bonds and notes	1,616,771		(85,913)		—		—		444	1,616,771		(85,913)
Agency CMO	55,693		(4,640)		4,272		(379)		39	59,965		(5,019)
Agency MBS	1,641,544		(206,412)		515,206		(96,927)		460	2,156,750		(303,339)
Agency CMBS	485,333		(68,674)		921,153		(189,440)		132	1,406,486		(258,114)
CMBS	273,150		(8,982)		598,490		(23,966)		52	871,640		(32,948)
CLO	—		—		2,107		(1)		1	2,107		(1)
Corporate debt	692,990		(89,692)		8,421		(1,895)		105	701,411		(91,587)
Private label MBS	44,249		(4,646)		—		—		3	44,249		(4,646)
Other	12,198		(350)		—		—		4	12,198		(350)
Total	$	5,417,865	$	(532,120)	$	2,429,126	$	(332,369)	1,282	$	7,846,991	$	(864,489)

The $18.5 million increase in gross unrealized losses from December 31, 2022, to June 30, 2023, is primarily due to higher market rates. The Company assesses each available-for-sale security that is in an unrealized loss position to determine whether the decline in fair value below the amortized cost basis is a result from a credit loss or other factors. At both June 30, 2023, and December 31, 2022, no ACL was recorded on available-for-sale securities as each of the securities in the Company's portfolio are investment grade, current as to principal and interest, and their price changes are consistent with interest and credit spreads when adjusting for convexity, rating, and industry differences.

At June 30, 2023, based on current market conditions and the Company's current targeted balance sheet composition strategy, the Company intends to hold its available-for-sale securities with unrealized loss positions through the anticipated recovery period, and it is more-likely-than-not that the Company will not have to sell these available-for-sale securities before the recovery of the entire amortized cost basis. The issuers of these available-for-sale securities have not, to the Company’s knowledge, established any cause for default. Market prices are expected to approach par as the securities approach maturity.

The following table summarizes the amortized cost and fair value of available-for-sale securities by contractual maturity:


	At June 30, 2023
(In thousands)	Amortized Cost		Fair Value
Maturing within 1 year	$	33,337	$	33,164
After 1 year through 5 years	1,040,297		978,096
After 5 through 10 years	1,401,731		1,277,563
After 10 years	6,166,939		5,470,518
Total available-for-sale securities	$	8,642,304	$	7,759,341

Available-for-sale securities that are not due at a single maturity date have been categorized based on the maturity date of the underlying collateral. Actual principal cash flows may differ from this categorization as borrowers have the right to repay their obligations with or without prepayment penalties.

During the three and six months ended June 30, 2023, the Company sold U.S. Treasury notes, Corporate debt securities, and Municipal bonds and notes classified as available-for-sale for proceeds of $2.9 million and $398.3 million, respectively, which resulted in gross realized losses of $48 thousand and $20.5 million, respectively. Because $3.8 million of the total loss recognized for the six months ended June 30, 2023, was attributed to a decline in credit quality, those portions of the charges have been included in the Provision for credit losses on the accompanying Condensed Consolidated Statements of Income. There were no sales of available-for-sale securities during the three and six months ended June 30, 2022.


	At June 30, 2023
(In thousands)	Amortized Cost (1)		Unrealized Gains		Unrealized Losses		Fair Value		Allowance		Net Carrying Value
Agency CMO	$	25,791	$	—	$	(2,133)	$	23,658	$	—	$	25,791
Agency MBS	2,541,384		524		(325,432)		2,216,476		—		2,541,384
Agency CMBS	3,353,205		—		(505,510)		2,847,695		—		3,353,205
Municipal bonds and notes	919,112		798		(36,263)		883,647		216		918,896
CMBS	104,508		—		(9,302)		95,206		—		104,508
Total held-to-maturity securities	$	6,944,000	$	1,322	$	(878,640)	$	6,066,682	$	216	$	6,943,784


	At December 31, 2022
(In thousands)	Amortized Cost (1)		Unrealized Gains		Unrealized Losses		Fair Value		Allowance		Net Carrying Value
Agency CMO	$	28,358	$	—	$	(2,060)	$	26,298	$	—	$	28,358
Agency MBS	2,626,114		827		(339,592)		2,287,349		—		2,626,114
Agency CMBS	2,831,949		845		(407,648)		2,425,146		—		2,831,949
Municipal bonds and notes	928,845		1,098		(47,183)		882,760		182		928,663
CMBS	149,613		—		(9,713)		139,900		—		149,613
Total held-to-maturity securities	$	6,564,879	$	2,770	$	(806,196)	$	5,761,453	$	182	$	6,564,697

(1)Accrued interest receivable on held-to-maturity securities of $24.5 million and $24.2 million at June 30, 2023, and December 31, 2022, respectively, is excluded from amortized cost and is included in Accrued interest receivable and other assets on the accompanying Condensed Consolidated Balance Sheets.

An ACL on held-to-maturity securities is recorded for certain Municipal bonds and notes to account for expected lifetime credit losses. Agency securities represent obligations issued by a U.S. government-sponsored enterprise or other federally-related entity and are either explicitly or implicitly guaranteed and therefore, assumed to be zero loss. Held-to-maturity securities with gross unrealized losses and no ACL are considered to be high credit quality, and therefore, zero credit loss has been recorded.

The following table summarizes the activity in the ACL on held-to-maturity securities:


	Three months ended June 30,				Six months ended June 30,
(In thousands)	2023		2022		2023		2022
Balance, beginning of period	$	282	$	204	$	182	$	214

(Benefit) provision for credit losses	(66)		6		34		(4)
Balance, end of period	$	216	$	210	$	216	$	210

The following table summarizes the amortized cost and fair value of held-to-maturity securities by contractual maturity:


	At June 30, 2023
(In thousands)	Amortized Cost		Fair Value
Maturing within 1 year	$	4,341	$	4,340
After 1 year through 5 years	55,954		56,141
After 5 through 10 years	344,666		326,276
After 10 years	6,539,039		5,679,925
Total held-to-maturity securities	$	6,944,000	$	6,066,682

Held-to-maturity securities that are not due at a single maturity date have been categorized based on the maturity date of the underlying collateral. Actual principal cash flows may differ from this categorization as borrowers have the right to prepay their obligations with or without prepayment penalties.

The Company monitors the credit quality of held-to-maturity securities through credit ratings provided by Standard & Poor's Rating Services, Moody's Investor Services, Fitch Ratings, Inc., Kroll Bond Rating Agency, or DBRS Inc. Credit ratings express opinions about the credit quality of a security, and are updated at each quarter end. Investment grade securities are rated BBB- or higher by S&P, or Baa3 or higher by Moody's, and are generally considered by the rating agencies and market participants to be of low credit risk. Conversely, securities rated below investment grade, which are labeled as speculative grade by the rating agencies, are considered to have distinctively higher credit risk than investment grade securities. There were no speculative grade held-to-maturity securities at June 30, 2023, or December 31, 2022. Held-to-maturity securities that are not rated are collateralized with U.S. Treasury obligations.

The following tables summarize the amortized cost of held-to-maturity securities based on their lowest publicly available credit rating:


	June 30, 2023
	Investment Grade
(In thousands)	Aaa		Aa1		Aa2		Aa3		A1		A2		A3		Not Rated
Agency CMO	$	—	$	25,791	$	—	$	—	$	—	$	—	$	—	$	—
Agency MBS	—		2,541,384		—		—		—		—		—		—
Agency CMBS	—		3,353,205		—		—		—		—		—		—
Municipal bonds and notes	334,490		162,966		254,457		116,030		32,949		—		4,165		14,055
CMBS	104,508		—		—		—		—		—		—		—
Total held-to-maturity securities	$	438,998	$	6,083,346	$	254,457	$	116,030	$	32,949	$	—	$	4,165	$	14,055


	December 31, 2022
	Investment Grade
(In thousands)	Aaa		Aa1		Aa2		Aa3		A1		A2		A3		Not Rated
Agency CMO	$	—	$	28,358	$	—	$	—	$	—	$	—	$	—	$	—
Agency MBS	—		2,626,114		—		—		—		—		—		—
Agency CMBS	—		2,831,949		—		—		—		—		—		—
Municipal bonds and notes	336,035		163,312		255,235		116,870		38,177		4,165		—		15,051
CMBS	149,613		—		—		—		—		—		—		—
Total held-to-maturity securities	$	485,648	$	5,649,733	$	255,235	$	116,870	$	38,177	$	4,165	$	—	$	15,051