Financial Guarantee Liability - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Guarantor Obligations
Outstanding loan balances	$ 24,000,000	$ 20,200,000
Maximum loss potential	7,200,000	5,800,000
Portion covered by Credit Enhancement Agreement	6,200	$ 9,800
Provision for expected credit losses	11,631
Delinquent
Guarantor Obligations
Outstanding loan balances	53,500
Maximum loss potential	$ 17,800
Number of loans (loans) | loan	4
Liquidation value of loans outstanding	$ 39,000
Potential loss on liquidation of loan	$ 5,300
Fannie Mae DUS or Freddie TAH Loans | Maximum
Guarantor Obligations
Percentage of contingent liability of actual losses incurred on outstanding loans (in percentage)	33.00%