Underwriting Information - Gross Written Premiums by Product (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Gross written premiums
Amount	$ 83,807	$ 58,346	$ 155,301	$ 112,377
% of GWP	100.00%	100.00%	100.00%	100.00%
Residential Earthquake
Gross written premiums
Amount	$ 34,240	$ 29,987	$ 62,996	$ 59,294
% of GWP	40.90%	51.40%	40.60%	52.80%
Commercial All Risk
Gross written premiums
Amount	$ 14,841	$ 7,288	$ 27,297	$ 14,852
% of GWP	17.70%	12.50%	17.60%	13.20%
Commercial Earthquake
Gross written premiums
Amount	$ 11,818	$ 8,085	$ 22,666	$ 14,618
% of GWP	14.10%	13.80%	14.60%	13.00%
Specialty Homeowners
Gross written premiums
Amount	$ 11,568	$ 8,646	$ 21,413	$ 16,426
% of GWP	13.80%	14.80%	13.80%	14.60%
Inland Marine
Gross written premiums
Amount	$ 3,451	$ 229	$ 5,341	$ 229
% of GWP	4.10%	0.40%	3.40%	0.20%
Hawaii Hurricane
Gross written premiums
Amount	$ 3,242	$ 2,675	$ 5,937	$ 4,750
% of GWP	3.90%	4.60%	3.80%	4.20%
Residential Flood
Gross written premiums
Amount	$ 2,032	$ 1,271	$ 3,558	$ 2,043
% of GWP	2.40%	2.20%	2.30%	1.80%
Other
Gross written premiums
Amount	$ 2,615	$ 165	$ 6,093	$ 165
% of GWP	3.10%	0.30%	3.90%	0.20%