Revenue - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) loan	Sep. 30, 2020 USD ($) loan	Sep. 30, 2021 USD ($) loan	Dec. 31, 2020 USD ($)
Contract With Customer Asset And Liability [Line Items]
Current contract assets	$ 60,739,000		$ 60,739,000	$ 50,386,000
Non-current contract assets	53,523,000		53,523,000	$ 38,956,000
Increase of contract assets due to new business generation	51,371,000		139,605,000
Adjustment of contract assets due to estimation of revenue from performance obligations satisfied in previous periods	7,515,000		24,414,000
Payments received from insurance carriers	35,360,000		82,999,000
Profit share
Contract With Customer Asset And Liability [Line Items]
Increase of contract assets due to new business generation	$ 27,932,000	$ 14,700,000	$ 77,605,000
Number of new certified loans | loan	49,332	20,696	129,058
Contract with customer, asset, average price per loan	$ 566	$ 711	$ 601
Estimated future profit share recorded	7,500,000	$ 3,800,000
Adjustment of contract assets due to estimation of revenue from performance obligations satisfied in previous periods	7,515,000		24,414,000
Payments received from insurance carriers	33,678,000		78,541,000
Profit share | COVID-19
Contract With Customer Asset And Liability [Line Items]
Payments received from insurance carriers	$ 33,700,000		$ 78,500,000