Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Schedule of Goodwill and Intangible Assets

	March 31,		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 $3,980 at 3/31/21 and $3,878 at 12/31/20		55		157
Total intangibles	$	7,555	$	7,657
Total goodwill and intangibles	$	53,617	$	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 March 31, 2021						Ended March 31, 2020
	Income		Shares		Per Share		Income			Shares		Per Share
(in thousands, except per share data)	(Numerator)		(Denominator)		Amount		(Numerator)			(Denominator)		Amount
Basic EPS
Earnings (loss) available to common shareholders	$	73,012		45,178	$	1.62	$	(61,267	)		44,920	$	(1.36	)
Effect of Dilutive Securities
Stock options and restricted stock units		—		496				—			—
Diluted EPS
Earnings (loss) available to common shareholders	$	73,012		45,674	$	1.60	$	(61,267	)		44,920	$	(1.36	)
Anti-dilutive options excluded from diluted EPS				—							94

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

(in thousands)	For the Three Months
	Ended March 31,
Unrealized Gains/Losses on Available-for-Sale Securities	2021			2020
Beginning balance	$	108,714		$	52,473
Cumulative-effect adjustment of ASU 2016-13		—			22
Adjusted beginning balance	$	108,714		$	52,495
Other comprehensive loss before reclassifications		(43,795	)		(11,880	)
Amounts reclassified from accumulated other comprehensive earnings		(952	)		(1,151	)
Net current-period other comprehensive loss	$	(44,747	)	$	(13,031	)
Ending balance	$	63,967		$	39,464
Balance of securities for which an allowance for credit losses has been recognized in net earnings	$	463		$	5,727

Schedule of Effects of Reclassifications out of Accumulated Other Comprehensive Earnings

	Amount Reclassified from Accumulated Other
(in thousands)	Comprehensive Earnings
	For the Three Months
Component of Accumulated	Ended March 31,						Affected line item in the
Other Comprehensive Earnings	2021			2020			Statement of Earnings
Unrealized gains and losses on available-for-sale securities	$	1,183		$	2,306		Net realized gains
		22			(849	)	Credit losses presented within net realized gains
	$	1,205		$	1,457		Earnings (loss) before income taxes
		(253	)		(306	)	Income tax benefit (expense)
	$	952		$	1,151		Net earnings (loss)