Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Provision (reversal) for expected credit losses	$ 700	$ 1,100	$ 588	$ (5,200)	$ (3,592)
Guaranty liabilities	26,577		26,577		25,989	$ 29,581
Allowance for doubtful accounts, period increase	900	500	5,500	4,600
Allowance for doubtful accounts	22,000		22,000		16,700
Allowance for credit loss	3,800		$ 3,800		$ 3,800
Number of operating segments | segment			1
Revenues	$ 664,646	$ 788,125	$ 2,098,245	1,921,977
Commercial mortgage origination, net
New Accounting Pronouncements or Change in Accounting Principle
Revenues			$ 284,483	$ 254,372