Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	June 30,		December 31,
(in thousands)	2021		2020
Goodwill
Surety	$	40,816	$	40,816
Casualty		5,246		5,246
Total goodwill	$	46,062	$	46,062
Intangibles
Indefinite-lived intangibles - state insurance licenses		7,500		7,500
Definite-lived intangibles, net of accumulated amortization of $4,015 at 6/30/21 and $3,878 at 12/31/20		20		157
Total intangibles	$	7,520	$	7,657
Total goodwill and intangibles	$	53,582	$	53,719

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, 2021						Ended June 30, 2020
	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	$	81,815		45,226	$	1.81	$	92,166		44,951	$	2.05
Effect of Dilutive Securities
Stock options and restricted stock units		—		489				—		323
Diluted EPS
Earnings available to common shareholders	$	81,815		45,715	$	1.79	$	92,166		45,274	$	2.04
Anti-dilutive options excluded from diluted EPS				169						94
	For the Six Months						For the Six Months
	Ended June 30, 2021						Ended June 30, 2020
	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	$	154,827		45,202	$	3.43	$	30,899		44,936	$	0.69
Effect of Dilutive Securities
Stock options and restricted stock units		—		501				—		375
Diluted EPS
Earnings available to common shareholders	$	154,827		45,703	$	3.39	$	30,899		45,311	$	0.68
Anti-dilutive options excluded from diluted EPS				169						335

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

(in thousands)	For the Three Months						For the Six Months
	Ended June 30,						Ended June 30,
Unrealized Gains/Losses on Available-for-Sale Securities	2021			2020			2021			2020
Beginning balance	$	63,967		$	39,464		$	108,714		$	52,473
Cumulative-effect adjustment of ASU 2016-13		—			—			—			22
Adjusted beginning balance	$	63,967		$	39,464		$	108,714		$	52,495
Other comprehensive earnings (loss) before reclassifications		15,601			53,733			(28,194	)		41,853
Amounts reclassified from accumulated other comprehensive earnings		(424	)		(162	)		(1,376	)		(1,313	)
Net current-period other comprehensive earnings (loss)	$	15,177		$	53,571		$	(29,570	)	$	40,540
Ending balance	$	79,144		$	93,035		$	79,144		$	93,035
Balance of securities for which an allowance for credit losses has been recognized in net earnings							$	321		$	1,752

Schedule of Effects of Reclassifications out of Accumulated Other Comprehensive Earnings

	Amount Reclassified from Accumulated Other
(in thousands)	Comprehensive Earnings
	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	2021			2020			2021				2020				Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	366		$	312			$	1,549			$	2,618		Net realized gains (losses)
		171			(107	)			193				(956	)	Credit losses presented within net realized gains
	$	537		$	205			$	1,742			$	1,662		Earnings before income taxes
		(113	)		(43	)			(366	)			(349	)	Income tax expense
	$	424		$	162			$	1,376			$	1,313		Net earnings