Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Net deferred tax asset
Deferred tax assets	$ 29,577	$ 29,392
Deferred tax liabilities	(334,686)	(279,012)
Net deferred tax liability	(305,109)	(249,620)
Components of the net deferred tax asset
Contingency reserves	(300,281)	(261,855)
Unrealized (gain) loss on investments	(30,050)	(13,214)
Unearned premium reserve	15,192	16,641
Accrued expenses	4,202	3,391
Deferred policy acquisition costs	(3,571)	(3,298)
Unearned ceding commissions	2,951	3,227
Loss reserves	2,529	416
Nonvested shares	1,767	2,426
Start-up expenditures, net	1,137	1,410
Change in fair market value of derivatives	912	370
Fixed assets	880	1,502
Investments in limited partnerships	(561)	(400)
Prepaid expenses	(129)	(132)
Loss reserves - TCJA transition adjustment	(94)	(113)
Organizational expenditures	7	9
Net deferred tax liability	$ (305,109)	$ (249,620)