Underwriting Information - Gross Written Premiums by Product (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gross written premiums
Amount	$ 152,332	$ 102,967	$ 385,267	$ 258,268
% of GWP	100.00%	100.00%	100.00%	100.00%
Residential Earthquake
Gross written premiums
Amount	$ 50,075	$ 40,507	$ 128,165	$ 103,503
% of GWP	32.90%	39.30%	33.30%	40.10%
Commercial Earthquake
Gross written premiums
Amount	$ 27,433	$ 18,061	$ 66,052	$ 40,727
% of GWP	18.00%	17.50%	17.10%	15.80%
Specialty Homeowners
Gross written premiums
Amount	$ 19,881	$ 17,048	$ 53,018	$ 38,461
% of GWP	13.10%	16.60%	13.80%	14.90%
Inland Marine
Gross written premiums
Amount	$ 19,532	$ 4,406	$ 39,047	$ 9,747
% of GWP	12.80%	4.30%	10.10%	3.80%
Hawaii Hurricane
Gross written premiums
Amount	$ 8,996	$ 4,360	$ 22,921	$ 10,296
% of GWP	5.90%	4.20%	5.90%	4.00%
Commercial All Risk
Gross written premiums
Amount	$ 6,867	$ 12,467	$ 30,032	$ 39,765
% of GWP	4.50%	12.10%	7.80%	15.40%
Residential Flood
Gross written premiums
Amount	$ 3,228	$ 2,170	$ 8,377	$ 5,728
% of GWP	2.10%	2.10%	2.20%	2.20%
Other
Gross written premiums
Amount	$ 16,320	$ 3,948	$ 37,655	$ 10,041
% of GWP	10.70%	3.90%	9.80%	3.80%