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

3 Months Ended

Mar. 31, 2025

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	March 31,		December 31,
(in thousands)	2025		2024
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 March 31, 2025						Ended March 31, 2024
	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	$	63,214		91,770	$	0.69	$	127,900		91,368	$	1.40
Effect of Dilutive Securities
Stock options and restricted stock units		—		758				—		958
Diluted EPS
Earnings available to common shareholders	$	63,214		92,528	$	0.68	$	127,900		92,326	$	1.39
Anti-dilutive securities excluded from diluted EPS				48						—

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

(in thousands)	For the Three Months
	Ended March 31,
Unrealized Gains (Losses) on Available-for-Sale Securities	2025		2024
Beginning balance	$	(173,723)	$	(166,303)
Other comprehensive earnings (loss) before reclassifications		29,899		(13,275)
Amounts reclassified from accumulated other comprehensive earnings		131		604
Net current-period other comprehensive earnings (loss)	$	30,030	$	(12,671)
Ending balance	$	(143,693)	$	(178,974)
Balance of securities for which an allowance for credit losses has been recognized in net earnings		1,692		904

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
Component of Accumulated	Ended March 31,				Affected line item in the
Other Comprehensive Earnings (Loss)	2025		2024		Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	(205)	$	(834)	Net realized gains (losses)
		40		70	Credit gains (losses) presented within net realized gains
	$	(165)	$	(764)	Earnings (loss) before income taxes
		34		160	Income tax (expense) benefit
	$	(131)	$	(604)	Net earnings (loss)