Retroactive Insurance Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Net premiums earned	$ 238,993	$ 207,293	$ 426,351	$ 411,149
Net losses and loss adjustment expenses			350,252	$ 398,923	$ 711,846
Retroactive Insurance Contract
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Net premiums written			4,500
Net premiums earned			3,000
Net losses and loss adjustment expenses			2,900
Prospective coverage for retroactive insurance contract
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Net premiums written			2,200
Net premiums earned			700
Retroactive coverage for retroactive insurance contract
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Net premiums written			2,300
Net premiums earned			$ 2,300