Investments (Tables)

3 Months Ended

Mar. 31, 2023

Investments Debt And Equity Securities [Abstract]

Schedule of Disposition of Fixed Income and Equity Securities

Sales	Proceeds		Gross Realized				Net Realized
(in thousands)	From Sales		Gains		Losses		Gain (Loss)
2023
Fixed income securities - available-for-sale	$	3,790	$	35	$	(82)	$	(47)
Equity securities		3,501		2,417		(101)		2,316
2022
Fixed income securities - available-for-sale	$	8,832	$	117	$	(31)	$	86
Equity securities		15,726		5,901		—		5,901
Calls/Maturities			Gross Realized				Net Realized
(in thousands)	Proceeds		Gains		Losses		Gain (Loss)
2023
Fixed income securities - available-for-sale	$	190,305	$	35	$	(40)	$	(5)
2022
Fixed income securities - available-for-sale	$	71,974	$	20	$	(13)	$	7

Fair Value, Assets Measured on Recurring Basis

	As of March 31, 2023
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs
(in thousands)	(Level 1)		(Level 2)		(Level 3)		Total
Fixed income securities - available-for-sale
U.S. government	$	—	$	385,199	$	—	$	385,199
U.S. agency		—		73,659		—		73,659
Non-U.S. government & agency		—		5,952		—		5,952
Agency MBS		—		359,974		—		359,974
ABS/CMBS/MBS*		—		246,382		—		246,382
Corporate		—		1,030,739		52,761		1,083,500
Municipal		—		547,148		—		547,148
Total fixed income securities - available-for-sale	$	—	$	2,649,053	$	52,761	$	2,701,814
Equity securities		517,489		—		1,608		519,097
Total	$	517,489	$	2,649,053	$	54,369	$	3,220,911

	As of December 31, 2022
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs
(in thousands)	(Level 1)		(Level 2)		(Level 3)		Total
Fixed income securities - available-for-sale
U.S. government	$	—	$	454,021	$	—	$	454,021
U.S. agency		—		73,063		—		73,063
Non-U.S. government & agency		—		5,847		—		5,847
Agency MBS		—		331,806		—		331,806
ABS/CMBS/MBS*		—		240,736		—		240,736
Corporate		—		980,676		53,654		1,034,330
Municipal		—		527,147		—		527,147
Total fixed income securities - available-for-sale	$	—	$	2,613,296	$	53,654	$	2,666,950
Equity securities		496,731		39		1,612		498,382
Total	$	496,731	$	2,613,335	$	55,266	$	3,165,332

* Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities

Summary of Changes in Balance of Level 3 Securities

(in thousands)	Level 3 Securities
Balance as of January 1, 2023	$	55,266
Net realized and unrealized gains (losses)
Included in other comprehensive earnings (loss)		671
Sales / Calls / Maturities		(1,568)
Balance as of March 31, 2023	$	54,369
Change in unrealized gains (losses) during the period for Level 3 assets held at period-end - included in other comprehensive earnings (loss)	$	671

Schedule of Contractual Maturity of Securities

	March 31, 2023
(in thousands)	Amortized Cost		Fair Value
Due in one year or less	$	294,528	$	293,229
Due after one year through five years		904,163		865,507
Due after five years through 10 years		514,187		478,924
Due after 10 years		546,390		457,798
ABS/CMBS/MBS*		674,045		606,356
Total available-for-sale	$	2,933,313	$	2,701,814

* Asset-backed, commercial mortgage-backed and mortgage-backed securities

Schedule of Amortized Cost and Fair Value of Available-for-sale Securities

	March 31, 2023
	Cost or		Allowance		Gross		Gross
	Amortized		for Credit		Unrealized		Unrealized		Fair
(in thousands)	Cost		Losses		Gains		Losses		Value
U.S. government	$	391,336	$	—	$	130	$	(6,267)	$	385,199
U.S. agency		75,257		—		33		(1,631)		73,659
Non-U.S. government & agency		6,798		—		—		(846)		5,952
Agency MBS		395,736		—		547		(36,309)		359,974
ABS/CMBS/MBS*		278,309		(7)		145		(32,065)		246,382
Corporate		1,156,944		(458)		1,344		(74,330)		1,083,500
Municipal		628,933		—		2,441		(84,226)		547,148
Total Fixed Income	$	2,933,313	$	(465)	$	4,640	$	(235,674)	$	2,701,814
	December 31, 2022
	Cost or		Allowance		Gross		Gross
	Amortized		for Credit		Unrealized		Unrealized		Fair
(in thousands)	Cost		Losses		Gains		Losses		Value
U.S. government	$	462,884	$	—	$	8	$	(8,871)	$	454,021
U.S. agency		75,074		—		26		(2,037)		73,063
Non-U.S. government & agency		6,798		—		—		(951)		5,847
Agency MBS		373,687		—		336		(42,217)		331,806
ABS/CMBS/MBS*		276,126		(8)		62		(35,444)		240,736
Corporate		1,122,097		(331)		541		(87,977)		1,034,330
Municipal		628,607		—		1,265		(102,725)		527,147
Total Fixed Income	$	2,945,273	$	(339)	$	2,238	$	(280,222)	$	2,666,950

* Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities

Schedule of Debt Securities Available-for-sale Allowance for Credit Loss

	Three Months Ended March 31,
(in thousands)	2023		2022
Beginning balance	$	339	$	441
Increase to allowance from securities for which credit losses were not previously recorded		54		131
Reductions from intent to sell securities		—		(17)
Net increase (decrease) from securities that had an allowance at the beginning of the period		72		39
Balance as of March 31,	$	465	$	594

Schedule of Securities in an Unrealized Loss Position Segregated by Type and Length of Time in an Unrealized Loss Position

	March 31, 2023						December 31, 2022
(in thousands)	< 12 Mos.		12 Mos. & Greater		Total		< 12 Mos.		12 Mos. & Greater		Total
U.S. government
Fair value	$	258,557	$	60,288	$	318,845	$	399,361	$	8,828	$	408,189
Amortized cost		262,101		63,011		325,112		407,340		9,720		417,060
Unrealized loss	$	(3,544)	$	(2,723)	$	(6,267)	$	(7,979)	$	(892)	$	(8,871)
U.S. agency
Fair value	$	26,616	$	8,940	$	35,556	$	32,987	$	2,170	$	35,157
Amortized cost		27,208		9,979		37,187		34,627		2,567		37,194
Unrealized loss	$	(592)	$	(1,039)	$	(1,631)	$	(1,640)	$	(397)	$	(2,037)
Non-U.S. government
Fair value	$	2,631	$	3,322	$	5,953	$	3,626	$	2,221	$	5,847
Amortized cost		2,702		4,097		6,799		3,798		3,000		6,798
Unrealized Loss	$	(71)	$	(775)	$	(846)	$	(172)	$	(779)	$	(951)
Agency MBS
Fair value	$	88,920	$	227,228	$	316,148	$	197,252	$	117,851	$	315,103
Amortized cost		91,195		261,262		352,457		212,776		144,544		357,320
Unrealized loss	$	(2,275)	$	(34,034)	$	(36,309)	$	(15,524)	$	(26,693)	$	(42,217)
ABS/CMBS/MBS*
Fair value	$	25,033	$	212,917	$	237,950	$	96,754	$	136,149	$	232,903
Amortized cost		25,851		244,164		270,015		104,724		163,623		268,347
Unrealized loss	$	(818)	$	(31,247)	$	(32,065)	$	(7,970)	$	(27,474)	$	(35,444)
Corporate
Fair value	$	383,271	$	572,886	$	956,157	$	660,830	$	323,337	$	984,167
Amortized cost		393,475		637,012		1,030,487		697,437		374,707		1,072,144
Unrealized loss	$	(10,204)	$	(64,126)	$	(74,330)	$	(36,607)	$	(51,370)	$	(87,977)
Municipal
Fair value	$	56,404	$	364,970	$	421,374	$	228,827	$	204,324	$	433,151
Amortized cost		56,986		448,614		505,600		255,240		280,636		535,876
Unrealized loss	$	(582)	$	(83,644)	$	(84,226)	$	(26,413)	$	(76,312)	$	(102,725)
Total fixed income
Fair value	$	841,432	$	1,450,551	$	2,291,983	$	1,619,637	$	794,880	$	2,414,517
Amortized cost		859,518		1,668,139		2,527,657		1,715,942		978,797		2,694,739
Unrealized loss	$	(18,086)	$	(217,588)	$	(235,674)	$	(96,305)	$	(183,917)	$	(280,222)

* Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities

Schedule of Credit Quality Indicators for Investments in Unrealized Loss Positions

	Equivalent	Equivalent	(dollars in thousands)
NAIC	S&P	Moody’s	Amortized				Unrealized		Percent
Rating	Rating	Rating	Cost		Fair Value		Loss		to Total
1	AAA/AA/A	Aaa/Aa/A	$	2,031,998	$	1,837,626	$	(194,372)	82.5	%
2	BBB	Baa		396,016		360,851		(35,165)	14.9	%
3	BB	Ba		58,153		54,496		(3,657)	1.6	%
4	B	B		38,897		37,168		(1,729)	0.7	%
5	CCC	Caa		2,593		1,842		(751)	0.3	%
6	CC or lower	Ca or lower		—		—		—	0.0	%
		Total	$	2,527,657	$	2,291,983	$	(235,674)	100.0	%