Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2023

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	March 31,		December 31,
(in thousands)	2023		2022
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, 2023						Ended March 31, 2022
	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	$	98,811		45,530	$	2.17	$	47,923		45,306	$	1.06
Effect of Dilutive Securities
Stock options and restricted stock units		—		505				—		408
Diluted EPS
Earnings available to common shareholders	$	98,811		46,035	$	2.15	$	47,923		45,714	$	1.05
Anti-dilutive securities excluded from diluted EPS				—						214

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	2023		2022
Beginning balance	$	(229,076)	$	49,826
Other comprehensive earnings (loss) before reclassifications		36,254		(115,742)
Amounts reclassified from accumulated other comprehensive earnings		1,453		161
Net current-period other comprehensive earnings (loss)	$	37,707	$	(115,581)
Ending balance	$	(191,369)	$	(65,755)
Balance of securities for which an allowance for credit losses has been recognized in net earnings		1,841		607

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)	2023		2022		Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	(1,713)	$	(51)	Net realized gains (losses)
		(126)		(153)	Credit gains presented within net realized gains
	$	(1,839)	$	(204)	Earnings (loss) before income taxes
		386		43	Income tax (expense) benefit
	$	(1,453)	$	(161)	Net earnings (loss)