Summary of Significant Accounting Policies - Allowance for Credit Losses on Premium Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Beginning balance	$ 10,000	$ 1,445	$ 1,458
Provision during the period for expected credit losses	(893)	10,294	6,162
Write-off amounts during the period	(3,693)	(4,406)	(7,000)
Recoveries during the period of amounts previously written off	586	812	825
Ending balance	6,000	10,000	1,445
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Beginning balance	0	1,855	0
Ending balance		0	1,855
Cumulative Effect, Period of Adoption, Adjusted Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Beginning balance	$ 10,000	3,300	1,458
Ending balance		$ 10,000	$ 3,300