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

9 Months Ended

Sep. 30, 2023

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	September 30,		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 September 30, 2023						Ended September 30, 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	$	13,536		45,622	$	0.30	$	439,893		45,379	$	9.69
Effect of Dilutive Securities
Stock options and restricted stock units		—		443				—		396
Diluted EPS
Earnings available to common shareholders	$	13,536		46,065	$	0.29	$	439,893		45,775	$	9.61
Anti-dilutive securities excluded from diluted EPS				145						435
	For the Nine Months						For the Nine Months
	Ended September 30, 2023						Ended September 30, 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	$	189,999		45,581	$	4.17	$	485,577		45,347	$	10.71
Effect of Dilutive Securities
Stock options and restricted stock units		—		486				—		428
Diluted EPS
Earnings available to common shareholders	$	189,999		46,067	$	4.12	$	485,577		45,775	$	10.61
Anti-dilutive securities excluded from diluted EPS				145						459

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	2023		2022		2023		2022
Beginning balance	$	(211,090)	$	(163,318)	$	(229,076)	$	49,826
Other comprehensive earnings (loss) before reclassifications		(57,261)		(82,785)		(41,355)		(296,422)
Amounts reclassified from accumulated other comprehensive earnings		427		1,537		2,507		2,030
Net current-period other comprehensive earnings (loss)	$	(56,834)	$	(81,248)	$	(38,848)	$	(294,392)
Ending balance	$	(267,924)	$	(244,566)	$	(267,924)	$	(244,566)
Balance of securities for which an allowance for credit losses has been recognized in net earnings					$	2,005	$	1,520

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)	2023		2022		2023		2022		Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	(271)	$	(1,912)	$	(2,808)	$	(2,684)	Net realized gains (losses)
		(270)		(34)		(365)		115	Credit gains (losses) presented within net realized gains
	$	(541)	$	(1,946)	$	(3,173)	$	(2,569)	Earnings (loss) before income taxes
		114		409		666		539	Income tax (expense) benefit
	$	(427)	$	(1,537)	$	(2,507)	$	(2,030)	Net earnings (loss)