Underwriting Information - Gross Written Premiums by State (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%
California
Gross written premiums
Amount	$ 72,505	$ 52,960	$ 180,142	$ 124,131
% of GWP	47.60%	51.40%	46.80%	48.10%
Texas
Gross written premiums
Amount	$ 19,715	$ 20,460	$ 48,142	$ 55,047
% of GWP	13.00%	19.90%	12.50%	21.30%
Hawaii
Gross written premiums
Amount	$ 10,342	$ 5,097	$ 26,312	$ 11,990
% of GWP	6.80%	5.00%	6.80%	4.60%
Florida
Gross written premiums
Amount	$ 7,203	$ 685	$ 24,958	$ 685
% of GWP	4.70%	0.70%	6.50%	0.30%
Washington
Gross written premiums
Amount	$ 7,180	$ 4,340	$ 15,931	$ 10,002
% of GWP	4.70%	4.20%	4.10%	3.90%
Oregon
Gross written premiums
Amount	$ 3,964	$ 2,912	$ 9,686	$ 7,298
% of GWP	2.60%	2.80%	2.50%	2.80%
North Carolina
Gross written premiums
Amount	$ 3,719	$ 2,839	$ 11,871	$ 7,131
% of GWP	2.40%	2.80%	3.10%	2.80%
Illinois
Gross written premiums
Amount	$ 2,893	$ 1,575	$ 8,668	$ 4,416
% of GWP	1.90%	1.50%	2.20%	1.70%
Other States
Gross written premiums
Amount	$ 24,811	$ 12,099	$ 59,557	$ 37,568
% of GWP	16.30%	11.70%	15.50%	14.50%