Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) reinsurance_company insurance_company	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) reinsurance_company insurance_company	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Accounting Policies [Line Items]
Investment in variable interest entities	$ 28,600		$ 28,600		$ 26,900
Effective U.S. federal income tax expense (benefit) rate			24.90%	(23.70%)
Pre-tax income (loss)	10,261	$ 32,483	$ 23,789	$ (108,346)
Income tax expense (benefit)	2,597	11,640	5,920	(25,729)
Development on prior year loss reserves	(1,576)	(3,450)	5,228	166,684
Excess and Surplus Lines
Accounting Policies [Line Items]
Development on prior year loss reserves	$ (32)	$ (7,500)	$ (91)	$ 161,200
UNITED STATES
Accounting Policies [Line Items]
Number of insurance companies | insurance_company	5		5
BERMUDA
Accounting Policies [Line Items]
Number of insurance companies | reinsurance_company	2		2