Nature of Operations and Basis of Presentation - Deferred Policy Acquisition Costs (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Recorded asset at beginning of period	$ 87,094
Underwriting costs deferred	108,464
Amortization of deferred policy acquisition costs	(99,272)
Recorded asset at ending of period	$ 96,286