Reinsurance - Schedule of Net Reinsurance Balances Recoverable, After Consideration of Collateral, from Top Reinsurers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 706,248
Ceded Premiums Written	$ 289,821	$ 244,344	$ 204,665
Percent of Total Ceded Premium Written	100.00%
Reinsurance balances recoverable as a percentage of shareholder's equity, threshold for disclosure	2.00%
Reinsurer Concentration Risk | Reinsurance Recoverable
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	100.00%
Munich Re America / HSB | AM Best Rating, A+, Superior | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 102,632
Ceded Premiums Written	$ 34,462
Percent of Total Ceded Premium Written	11.90%
Munich Re America / HSB | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	14.50%
Renaissance Re | AM Best Rating, A+, Superior | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 58,417
Ceded Premiums Written	$ 25,001
Percent of Total Ceded Premium Written	8.60%
Renaissance Re | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	8.30%
Endurance Re | AM Best Rating, A+, Superior | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 47,136
Ceded Premiums Written	$ 9,865
Percent of Total Ceded Premium Written	3.40%
Endurance Re | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	6.70%
Scor Re | AM Best Rating, A+, Superior | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 37,160
Ceded Premiums Written	$ 13,398
Percent of Total Ceded Premium Written	4.60%
Scor Re | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	5.30%
Aspen UK Ltd. | AM Best Rating, A, Excellent | S&P Rating, A-, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 36,164
Ceded Premiums Written	$ 9,402
Percent of Total Ceded Premium Written	3.20%
Aspen UK Ltd. | Reinsurer Concentration Risk | AM Best Rating, A, Excellent | Reinsurance Recoverable | S&P Rating, A-, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	5.10%
Berkley Insurance Co. | AM Best Rating, A+, Superior | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 36,033
Ceded Premiums Written	$ 12,950
Percent of Total Ceded Premium Written	4.50%
Berkley Insurance Co. | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	5.10%
Hannover Ruckversicherung | AM Best Rating, A+, Superior | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 33,125
Ceded Premiums Written	$ 12,942
Percent of Total Ceded Premium Written	4.50%
Hannover Ruckversicherung | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, AA-, Very Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	4.70%
Safety National | AM Best Rating, A++, Superior | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 32,196
Ceded Premiums Written	$ 15,544
Percent of Total Ceded Premium Written	5.40%
Safety National | Reinsurer Concentration Risk | AM Best Rating, A++, Superior | Reinsurance Recoverable | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	4.60%
Nationwide Mutual | AM Best Rating, A+, Superior | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 29,818
Ceded Premiums Written	$ 17,738
Percent of Total Ceded Premium Written	6.10%
Nationwide Mutual | Reinsurer Concentration Risk | AM Best Rating, A+, Superior | Reinsurance Recoverable | S&P Rating, A+, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	4.20%
Liberty Mutual | AM Best Rating, A, Excellent | S&P Rating, A, Strong
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 23,236
Ceded Premiums Written	$ 7,240
Percent of Total Ceded Premium Written	2.50%
Liberty Mutual | Reinsurer Concentration Risk | AM Best Rating, A, Excellent | Reinsurance Recoverable | S&P Rating, A, Strong
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	3.30%
All Other Reinsurers
Ceded Credit Risk [Line Items]
Net Reinsurer Exposure	$ 270,331
Ceded Premiums Written	$ 131,279
Percent of Total Ceded Premium Written	45.30%
All Other Reinsurers | Reinsurer Concentration Risk | Reinsurance Recoverable
Ceded Credit Risk [Line Items]
Percent of Total Net Reinsurer Exposure	38.20%