Basis of Presentation and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	September 30,		December 31,
(in thousands)	2024		2023
Goodwill
Surety	$	40,816	$	40,816
Casualty		5,246		5,246
Total goodwill	$	46,062	$	46,062
Indefinite-lived intangibles		7,500		7,500
Total goodwill and intangibles	$	53,562	$	53,562

Schedule of Reconciliation of Numerator and Denominator of the Basic and Diluted Earnings Per Share Computations

	For the Three Months						For the Three Months
	Ended September 30, 2024						Ended September 30, 2023
	Income		Shares		Per Share		Income		Shares		Per Share
(in thousands, except per share data)	(Numerator)		(Denominator)		Amount		(Numerator)		(Denominator)		Amount
Basic EPS
Earnings available to common shareholders	$	95,027		45,780	$	2.08	$	13,536		45,622	$	0.30
Effect of Dilutive Securities
Stock options and restricted stock units		—		440				—		443
Diluted EPS
Earnings available to common shareholders	$	95,027		46,220	$	2.06	$	13,536		46,065	$	0.29
Anti-dilutive securities excluded from diluted EPS				24						145
	For the Nine Months						For the Nine Months
	Ended September 30, 2024						Ended September 30, 2023
	Income		Shares		Per Share		Income		Shares		Per Share
(in thousands, except per share data)	(Numerator)		(Denominator)		Amount		(Numerator)		(Denominator)		Amount
Basic EPS
Earnings available to common shareholders	$	304,919		45,734	$	6.67	$	189,999		45,581	$	4.17
Effect of Dilutive Securities
Stock options and restricted stock units		—		451				—		486
Diluted EPS
Earnings available to common shareholders	$	304,919		46,185	$	6.60	$	189,999		46,067	$	4.12
Anti-dilutive securities excluded from diluted EPS				24						145

Schedule of Changes in the Balance of Each Component of Accumulated Other Comprehensive Earnings (Loss)

(in thousands)	For the Three Months				For the Nine Months
	Ended September 30,				Ended September 30,
Unrealized Gains/Losses on Available-for-Sale Securities	2024		2023		2024		2023
Beginning balance	$	(186,817)	$	(211,090)	$	(166,303)	$	(229,076)
Other comprehensive earnings (loss) before reclassifications		79,210		(57,261)		57,364		(41,355)
Amounts reclassified from accumulated other comprehensive earnings		1,083		427		2,415		2,507
Net current-period other comprehensive earnings (loss)	$	80,293	$	(56,834)	$	59,779	$	(38,848)
Ending balance	$	(106,524)	$	(267,924)	$	(106,524)	$	(267,924)
Balance of securities for which an allowance for credit losses has been recognized in net earnings					$	1,813	$	2,005

Schedule of Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Loss)

	Amount Reclassified from Accumulated Other
(in thousands)	Comprehensive Earnings (Loss)
	For the Three Months				For the Nine Months
Component of Accumulated	Ended September 30,				Ended September 30,				Affected line item in the
Other Comprehensive Earnings (Loss)	2024		2023		2024		2023		Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	(1,365)	$	(271)	$	(3,129)	$	(2,808)	Net realized gains (losses)
		(6)		(270)		72		(365)	Credit gains (losses) presented within net realized gains
	$	(1,371)	$	(541)	$	(3,057)	$	(3,173)	Earnings (loss) before income taxes
		288		114		642		666	Income tax (expense) benefit
	$	(1,083)	$	(427)	$	(2,415)	$	(2,507)	Net earnings (loss)