

	December 31, 2023
	Amortized Cost		Gross Unrealized				Carrying Value (1)
			Gains		Losses
Investment securities available for sale:
U.S. Treasury securities	$	139,858	$	532	$	(9,798)	$	130,592
U.S. Government agency and sponsored enterprise residential MBS	1,962,658		1,810		(40,261)		1,924,207
U.S. Government agency and sponsored enterprise commercial MBS	561,557		107		(63,805)		497,859

Private label residential MBS and CMOs	2,596,231		268		(300,769)		2,295,730
Private label commercial MBS	2,282,833		678		(84,768)		2,198,743
Single family real estate-backed securities	383,984		—		(17,729)		366,255
Collateralized loan obligations	1,122,799		735		(10,710)		1,112,824
Non-mortgage asset-backed securities	106,095		156		(3,471)		102,780
State and municipal obligations	107,176		715		(5,273)		102,618
SBA securities	106,237		41		(3,254)		103,024

	9,369,428		$	5,042	$	(539,838)	8,834,632
Investment securities held to maturity	10,000						10,000
	$	9,379,428					8,844,632
Marketable equity securities							32,722
							$	8,877,354



	December 31, 2022
	Amortized Cost		Gross Unrealized				Carrying Value (1)
			Gains		Losses
Investment securities available for sale:
U.S. Treasury securities	$	148,956	$	63	$	(13,178)	$	135,841
U.S. Government agency and sponsored enterprise residential MBS	2,036,693		1,334		(54,859)		1,983,168
U.S. Government agency and sponsored enterprise commercial MBS	600,517		—		(75,423)		525,094

Private label residential MBS and CMOs	2,864,589		54		(333,980)		2,530,663
Private label commercial MBS	2,645,168		176		(120,990)		2,524,354
Single family real estate-backed securities	502,194		—		(31,753)		470,441
Collateralized loan obligations	1,166,838		151		(30,526)		1,136,463
Non-mortgage asset-backed securities	102,194		—		(6,218)		95,976
State and municipal obligations	122,181		695		(6,215)		116,661
SBA securities	139,320		381		(3,919)		135,782
	10,328,650		$	2,854	$	(677,061)	9,654,443
Investment securities held to maturity	10,000						10,000
	$	10,338,650					9,664,443
Marketable equity securities							90,884
							$	9,755,327

Investment securities held to maturity at December 31, 2023 and 2022, consisted of one State of Israel bond maturing in October 2024. Accrued interest receivable on investments totaled $37 million and $34 million at December 31, 2023 and 2022, respectively, and is included in other assets in the accompanying consolidated balance sheets.


	Years Ended December 31,
		2023		2022		2021

Gross realized gains on investment securities AFS		$	1,862	$	4,058	$	10,005
Gross realized losses on investment securities AFS		(47)		(131)		(995)
Net realized gain		1,815		3,927		9,010

Net losses on marketable equity securities recognized in earnings		(11,867)		(19,732)		(2,564)

Gain (loss) on investment securities, net		$	(10,052)	$	(15,805)	$	6,446

The following tables present the aggregate fair value and the aggregate amount by which amortized cost exceeded fair value for investment securities available for sale in unrealized loss positions aggregated by investment category and length of time that individual securities had been in continuous unrealized loss positions at the dates indicated (in thousands):


	December 31, 2023

	Less than 12 Months				12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury securities	$	9,941	$	(27)	$	99,769	$	(9,771)	$	109,710	$	(9,798)
U.S. Government agency and sponsored enterprise residential MBS	82,382		(430)		1,646,081		(39,831)		1,728,463		(40,261)
U.S. Government agency and sponsored enterprise commercial MBS	3,332		(6)		481,651		(63,799)		484,983		(63,805)

Private label residential MBS and CMOs	—		—		2,255,461		(300,769)		2,255,461		(300,769)
Private label commercial MBS	51,434		(323)		2,054,378		(84,445)		2,105,812		(84,768)
Single family real estate-backed securities	—		—		366,255		(17,729)		366,255		(17,729)
Collateralized loan obligations	184,652		(348)		880,609		(10,362)		1,065,261		(10,710)
Non-mortgage asset-backed securities	—		—		79,697		(3,471)		79,697		(3,471)
State and municipal obligations	24,765		(1,049)		32,380		(4,224)		57,145		(5,273)
SBA securities	8,194		(46)		89,763		(3,208)		97,957		(3,254)

	$	364,700	$	(2,229)	$	7,986,044	$	(537,609)	$	8,350,744	$	(539,838)


	December 31, 2022
	Less than 12 Months				12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury securities	$	29,198	$	(495)	$	86,744	$	(12,683)	$	115,942	$	(13,178)
U.S. Government agency and sponsored enterprise residential MBS	1,243,286		(26,789)		672,322		(28,070)		1,915,608		(54,859)
U.S. Government agency and sponsored enterprise commercial MBS	236,102		(5,736)		288,992		(69,687)		525,094		(75,423)

Private label residential MBS and CMOs	1,103,578		(93,480)		1,413,642		(240,500)		2,517,220		(333,980)
Private label commercial MBS	1,191,969		(39,729)		1,223,223		(81,261)		2,415,192		(120,990)
Single family real estate-backed securities	391,421		(22,293)		79,020		(9,460)		470,441		(31,753)
Collateralized loan obligations	596,803		(14,020)		494,945		(16,506)		1,091,748		(30,526)
Non-mortgage asset-backed securities	95,976		(6,218)		—		—		95,976		(6,218)
State and municipal obligations	67,444		(6,154)		1,114		(61)		68,558		(6,215)
SBA securities	42,900		(553)		74,291		(3,366)		117,191		(3,919)

	$	4,998,677	$	(215,467)	$	4,334,293	$	(461,594)	$	9,332,970	$	(677,061)

The Company monitors its investment securities available for sale for credit loss impairment on an individual security basis. No securities were determined to be credit loss impaired during the years ended December 31, 2023, 2022 and 2021. At December 31, 2023, the Company did not have an intent to sell securities that were in unrealized loss positions, and it was not more likely than not that the Company would be required to sell these securities before recovery of the amortized cost basis, which may be at maturity. In making this determination, the Company considered its current and projected liquidity position including its ability to pledge securities to generate liquidity, its investment policy as to permissible holdings and concentration limits, regulatory requirements and other relevant factors. While events of early 2023 impacting the banking sector impacted the liquidity profile of many banks, including BankUnited, the substantial majority of our investment securities are pledgeable at either the FHLB or FRB. We have not sold, and do not anticipate the need to sell, securities in unrealized loss positions to generate liquidity.

At December 31, 2023, 558 securities available for sale were in unrealized loss positions. The amount of impairment related to 114 of these securities was considered insignificant both individually and in the aggregate, totaling approximately $1.1 million and no further analysis with respect to these securities was considered necessary.

Unrealized losses were primarily attributable to a sustained higher interest rate environment. In some cases, wider spreads compared to levels at which securities were purchased. market volatility and yield curve dislocations also contributed to unrealized losses, particularly in the CLO segment. The investment securities AFS portfolio was in a net unrealized loss position of $534.8 million at December 31, 2023, compared to $674.2 million at December 31, 2022, improving by $139.4 million during the year ended December 31, 2023. While the majority of securities in the portfolio were floating rate at December 31, 2023, fixed rate securities accounted for the majority of unrealized losses.

At December 31, 2023, six U.S. treasury, 130 U.S. Government agency and sponsored enterprise residential MBS, 26 U.S. Government agency and sponsored enterprise commercial MBS, and 22 SBA securities were in unrealized loss positions. The timely payment of principal and interest on these securities is explicitly or implicitly guaranteed by the U.S. Government. As such, there is an assumption of zero credit loss and the Company expects to recover the amortized cost basis of these securities.

None of the impaired private label securities had missed principal or interest payments or had been downgraded by a NRSRO at December 31, 2023. The Company performed an analysis comparing the present value of cash flows expected to be collected to the amortized cost basis of impaired securities. This analysis was based on a scenario that we believe to be generally more conservative than our reasonable and supportable economic forecast at December 31, 2023, and incorporated assumptions about voluntary prepayment rates, collateral defaults, delinquencies, severity and other relevant factors as described further below. Our analysis also considered the structural characteristics of each security and the level of credit enhancement provided by that structure.

At December 31, 2023, 114 private label residential MBS and CMOs were in unrealized loss positions. Our analysis of cash flows expected to be collected on these securities incorporated assumptions about collateral default rates, voluntary prepayment rates, loss severity, delinquencies and recovery lag. In developing those assumptions, we took into account collateral quality measures such as FICO, LTV, documentation, loan type, property type, agency availability criteria and performing status. We also regularly monitor sector data including home price appreciation, forbearance, delinquency, special servicing and prepay trends as well as other economic data that could be indicative of stress in the sector. Underlying delinquencies in this sector remain low. Our December 31, 2023 analysis projected weighted average collateral losses for impaired securities in this category of 2% compared to weighted average credit support of 18%. As of December 31, 2023, 95% of impaired securities in this category, based on carrying value, were externally rated AAA, 4% were rated AA and 1% were rated A.

At December 31, 2023, 95 private label commercial MBS were in unrealized loss positions. Our analysis of cash flows expected to be collected on these securities incorporated assumptions about collateral default rates, voluntary prepayment rates, loss severity, delinquencies and recovery lag. In developing those assumptions, we took into account collateral quality and type, loan size, loan purpose and other qualitative factors. We also regularly monitor collateral concentrations, collateral watch lists, bankruptcy data, defeasance data, special servicing trends, delinquency and other economic data that could be indicative of stress in the sector. We consider collateral, deal, sector and tranche level performance as well as maturity and refinance risk. While we have observed some deterioration in collateral performance in this segment, particularly in the office, retail and hospitality sectors, the high credit quality of these securities and adequacy of subordination to cover projected collateral losses supports the conclusion that there is no credit loss impairment. Our December 31, 2023 analysis projected weighted average collateral losses for impaired securities in this category of 7% compared to weighted average credit support of 43%. As of December 31, 2023, 85% of impaired securities in this category, based on carrying value, were externally rated AAA, 11% were rated AA and 4% were rated A.

At December 31, 2023, 13 single family rental real estate-backed securities were in unrealized loss positions. Our analysis of cash flows expected to be collected on these securities incorporated assumptions about collateral default rates, loss severity, delinquencies and recovery lag. We regularly monitor sector data including home price appreciation, forbearance, delinquency and prepay trends as well as other economic data that could be indicative of stress in the sector. We consider collateral, deal, sector and tranche level performance as well as maturity and refinance risk. Our December 31, 2023 analysis projected weighted average collateral losses for this category of 8% compared to weighted average credit support of 53%. As of December 31, 2023, 57% of impaired securities in this category, based on carrying value, were externally rated AAA, 17% were rated AA and one security was not externally rated.

At December 31, 2023, 28 collateralized loan obligations were in unrealized loss positions. Unrealized losses totaled less than 1% of total amortized cost of this segment at December 31, 2023. Our analysis of cash flows expected to be collected on these securities incorporated assumptions about collateral default rates, loss severity, and delinquencies, calibrated to take into account idiosyncratic risks associated with the underlying collateral. In developing those assumptions, we took into account each sector’s performance pre-, during and post the 2008 financial crisis. We regularly engage with bond managers to monitor

trends in underlying collateral including potential downgrades and subsequent cash flow diversions, liquidity, ratings migration, and any other relevant developments. While we have observed some deterioration in underlying collateral performance due in large part to rising costs, the high credit quality of these securities and adequacy of subordination to cover projected collateral losses supports the conclusion that there is no credit loss impairment. Our December 31, 2023 analysis projected weighted average collateral losses for impaired securities in this category of 15% compared to weighted average credit support of 45%. As of December 31, 2023, 81% of the impaired securities in this category, based on carrying value, were externally rated AAA, 15% were rated AA and 4% were rated A.

At December 31, 2023, six non-mortgage asset-backed securities were in unrealized loss positions. These securities are backed by student loan collateral. Our analysis of cash flows expected to be collected on these securities incorporated assumptions about collateral default rates, loss severity, delinquencies, voluntary prepayment rates and recovery lag. In developing assumptions, we took into account collateral type, delineated by whether collateral consisted of loans to borrowers in school, refinancing, or a mixture. Our December 31, 2023 analysis projected weighted average collateral losses for impaired securities in this category of 4% compared to weighted average credit support of 24%. As of December 31, 2023, 38% of the impaired securities in this category, based on carrying value, were externally rated AAA, and 62% were rated AA.

At December 31, 2023, four state and municipal obligations were in unrealized loss positions. Our analysis of potential credit loss impairment for these securities incorporates a quantitative measure of the underlying obligor's credit worthiness provided by a third-party vendor as well as other relevant qualitative considerations. As of December 31, 2023, 98% of the impaired securities in this category, based on carrying value, were externally rated AAA and 2% were rated AA.