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

6 Months Ended

Jun. 30, 2024

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	June 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 June 30, 2024						Ended June 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	$	81,992		45,737	$	1.79	$	77,652		45,591	$	1.70
Effect of Dilutive Securities
Stock options and restricted stock units		—		442				—		453
Diluted EPS
Earnings available to common shareholders	$	81,992		46,179	$	1.78	$	77,652		46,044	$	1.69
Anti-dilutive securities excluded from diluted EPS				—						118
	For the Six Months						For the Six Months
	Ended June 30, 2024						Ended June 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	$	209,892		45,709	$	4.59	$	176,463		45,560	$	3.87
Effect of Dilutive Securities
Stock options and restricted stock units		—		460				—		485
Diluted EPS
Earnings available to common shareholders	$	209,892		46,169	$	4.55	$	176,463		46,045	$	3.83
Anti-dilutive securities excluded from diluted EPS				114						118

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

(in thousands)	For the Three Months				For the Six Months
	Ended June 30,				Ended June 30,
Unrealized Gains/Losses on Available-for-Sale Securities	2024		2023		2024		2023
Beginning balance	$	(178,974)	$	(191,369)	$	(166,303)	$	(229,076)
Other comprehensive earnings (loss) before reclassifications		(8,571)		(20,347)		(21,846)		15,908
Amounts reclassified from accumulated other comprehensive earnings		728		626		1,332		2,078
Net current-period other comprehensive earnings (loss)	$	(7,843)	$	(19,721)	$	(20,514)	$	17,986
Ending balance	$	(186,817)	$	(211,090)	$	(186,817)	$	(211,090)
Balance of securities for which an allowance for credit losses has been recognized in net earnings					$	1,463	$	1,053

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 Six Months
Component of Accumulated	Ended June 30,				Ended June 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	$	(931)	$	(824)	$	(1,765)	$	(2,536)	Net realized gains (losses)
		9		31		79		(95)	Credit gains (losses) presented within net realized gains
	$	(922)	$	(793)	$	(1,686)	$	(2,631)	Earnings (loss) before income taxes
		194		167		354		553	Income tax (expense) benefit
	$	(728)	$	(626)	$	(1,332)	$	(2,078)	Net earnings (loss)