Underwriting Information - Gross Written Premiums by Product (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Gross written premiums
Amount	$ 250,112	$ 170,934
% of GWP	100.00%	100.00%
Fronting Premiums
Gross written premiums
Amount	$ 91,755	$ 29,845
% of GWP	36.70%	17.50%
Residential Earthquake
Gross written premiums
Amount	$ 55,725	$ 46,336
% of GWP	22.30%	27.10%
Commercial Earthquake
Gross written premiums
Amount	$ 37,770	$ 25,144
% of GWP	15.10%	14.70%
Inland Marine
Gross written premiums
Amount	$ 31,049	$ 18,237
% of GWP	12.40%	10.70%
Casualty
Gross written premiums
Amount	$ 11,733	$ 5,007
% of GWP	4.70%	2.90%
Commercial All Risk
Gross written premiums
Amount	$ 8,376	$ 11,210
% of GWP	3.30%	6.60%
Hawaii Hurricane
Gross written premiums
Amount	$ 8,073	$ 6,914
% of GWP	3.20%	4.00%
Residential Flood
Gross written premiums
Amount	$ 4,235	$ 2,993
% of GWP	1.70%	1.80%
Specialty Homeowners
Gross written premiums
Amount		$ 16,284
Amount, net	$ (59)
% of GWP		9.50%
Others
Gross written premiums
Amount	$ 1,455	$ 8,964
% of GWP	0.60%	5.20%