Reinsurance - Summary of Quota Reinsurance Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Effects of Reinsurance [Line Items]
Ceded losses incurred	$ 20,707	$ 2,736	$ 65,462	$ 7,841
Reinsurance recoverable on loss reserves	83,143	19,566	83,143	19,566	$ 21,641	$ 33,328
Quota Share Reinsurance Agreements, Excluding Captive Agreements
Effects of Reinsurance [Line Items]
Ceded premiums written and earned, net of profit commission	43,448	23,032	131,651	87,721
Ceded losses incurred	20,707	2,729	65,493	7,845
Ceding commissions	12,128	11,042	35,518	37,807
Profit commission	17,191	$ 32,177	45,939	108,079
Reinsurance recoverable on loss reserves	$ 83,100		$ 83,100		$ 21,600
Quota Share Reinsurance Agreement, 2015
Effects of Reinsurance [Line Items]
Contingent termination fee				$ 6,800