Investments (Tables)

6 Months Ended

Jun. 30, 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	$	20,729	$	99	$	(910)	$	(811)
Equity securities		22,029		8,841		(101)		8,740
2022
Fixed income securities - available-for-sale	$	19,390	$	215	$	(432)	$	(217)
Equity securities		53,525		19,244		(15)		19,229
Calls/Maturities			Gross Realized				Net Realized
(in thousands)	Proceeds		Gains		Losses		Gain (Loss)
2023
Fixed income securities - available-for-sale	$	349,734	$	37	$	(43)	$	(6)
2022
Fixed income securities - available-for-sale	$	137,499	$	76	$	(55)	$	21

Fair Value, Assets Measured on Recurring Basis

	As of June 30, 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	$	—	$	315,976	$	—	$	315,976
U.S. agency		—		43,719		—		43,719
Non-U.S. government & agency		—		3,960		—		3,960
Agency MBS		—		372,030		—		372,030
ABS/CMBS/MBS*		—		252,330		—		252,330
Corporate		—		1,095,038		52,466		1,147,504
Municipal		—		553,581		—		553,581
Total fixed income securities - available-for-sale	$	—	$	2,636,634	$	52,466	$	2,689,100
Equity securities		550,986		—		1,580		552,566
Total	$	550,986	$	2,636,634	$	54,046	$	3,241,666

	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)		551
Sales / Calls / Maturities		(1,771)
Balance as of June 30, 2023	$	54,046
Change in unrealized gains (losses) during the period for Level 3 assets held at period-end - included in other comprehensive earnings (loss)	$	551

Schedule of Contractual Maturity of Securities

	June 30, 2023
(in thousands)	Amortized Cost		Fair Value
Due in one year or less	$	195,245	$	193,554
Due after one year through five years		910,005		861,351
Due after five years through 10 years		567,327		529,864
Due after 10 years		573,985		479,971
ABS/CMBS/MBS*		700,358		624,360
Total available-for-sale	$	2,946,920	$	2,689,100

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

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

	June 30, 2023
	Cost or		Allowance		Gross		Gross
	Amortized		for Credit		Unrealized		Unrealized		Fair
(in thousands)	Cost		Losses		Gains		Losses		Value
U.S. government	$	325,893	$	—	$	—	$	(9,917)	$	315,976
U.S. agency		45,937		—		—		(2,218)		43,719
Non-U.S. government & agency		4,799		—		—		(839)		3,960
Agency MBS		414,503		—		206		(42,679)		372,030
ABS/CMBS/MBS*		285,855		(5)		78		(33,598)		252,330
Corporate		1,227,628		(429)		1,872		(81,567)		1,147,504
Municipal		642,305		—		1,397		(90,121)		553,581
Total Fixed Income	$	2,946,920	$	(434)	$	3,553	$	(260,939)	$	2,689,100
	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 June 30,				Six Months Ended June 30,
(in thousands)	2023		2022		2023		2022
Beginning balance	$	465	$	594	$	339	$	441
Increase to allowance from securities for which credit losses were not previously recorded		2		149		25		223
Reduction from securities sold during the period		—		(433)		—		(433)
Reductions from intent to sell securities		—		—		—		(17)
Net increase (decrease) from securities that had an allowance at the beginning of the period		(33)		(18)		70		78
Balance as of June 30,	$	434	$	292	$	434	$	292

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

	June 30, 2023						December 31, 2022
(in thousands)	< 12 Mos.		12 Mos. & Greater		Total		< 12 Mos.		12 Mos. & Greater		Total
U.S. government
Fair value	$	220,227	$	95,748	$	315,975	$	399,361	$	8,828	$	408,189
Amortized cost		225,987		99,905		325,892		407,340		9,720		417,060
Unrealized loss	$	(5,760)	$	(4,157)	$	(9,917)	$	(7,979)	$	(892)	$	(8,871)
U.S. agency
Fair value	$	33,951	$	9,768	$	43,719	$	32,987	$	2,170	$	35,157
Amortized cost		34,975		10,962		45,937		34,627		2,567		37,194
Unrealized loss	$	(1,024)	$	(1,194)	$	(2,218)	$	(1,640)	$	(397)	$	(2,037)
Non-U.S. government
Fair value	$	658	$	3,302	$	3,960	$	3,626	$	2,221	$	5,847
Amortized cost		702		4,097		4,799		3,798		3,000		6,798
Unrealized Loss	$	(44)	$	(795)	$	(839)	$	(172)	$	(779)	$	(951)
Agency MBS
Fair value	$	141,545	$	216,878	$	358,423	$	197,252	$	117,851	$	315,103
Amortized cost		146,150		254,952		401,102		212,776		144,544		357,320
Unrealized loss	$	(4,605)	$	(38,074)	$	(42,679)	$	(15,524)	$	(26,693)	$	(42,217)
ABS/CMBS/MBS*
Fair value	$	20,483	$	219,639	$	240,122	$	96,754	$	136,149	$	232,903
Amortized cost		21,028		252,692		273,720		104,724		163,623		268,347
Unrealized loss	$	(545)	$	(33,053)	$	(33,598)	$	(7,970)	$	(27,474)	$	(35,444)
Corporate
Fair value	$	429,215	$	607,324	$	1,036,539	$	660,830	$	323,337	$	984,167
Amortized cost		441,843		676,263		1,118,106		697,437		374,707		1,072,144
Unrealized loss	$	(12,628)	$	(68,939)	$	(81,567)	$	(36,607)	$	(51,370)	$	(87,977)
Municipal
Fair value	$	131,486	$	362,776	$	494,262	$	228,827	$	204,324	$	433,151
Amortized cost		133,340		451,043		584,383		255,240		280,636		535,876
Unrealized loss	$	(1,854)	$	(88,267)	$	(90,121)	$	(26,413)	$	(76,312)	$	(102,725)
Total fixed income
Fair value	$	977,565	$	1,515,435	$	2,493,000	$	1,619,637	$	794,880	$	2,414,517
Amortized cost		1,004,025		1,749,914		2,753,939		1,715,942		978,797		2,694,739
Unrealized loss	$	(26,460)	$	(234,479)	$	(260,939)	$	(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	$	2,269,819	$	2,052,151	$	(217,668)	83.4	%
2	BBB	Baa		404,162		366,729		(37,433)	14.4	%
3	BB	Ba		45,298		41,464		(3,834)	1.5	%
4	B	B		32,264		30,844		(1,420)	0.5	%
5	CCC	Caa		2,396		1,812		(584)	0.2	%
6	CC or lower	Ca or lower		—		—		—	0.0	%
		Total	$	2,753,939	$	2,493,000	$	(260,939)	100.0	%