Financial Guarantee Liability - Summary of Changes on Estimated Liability Under Guarantee Liability (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Guaranty LIability:
Beginning balance		$ 15,000
Provision for expected credit losses	$ 0	14,702,000
Ending balance	$ 32,652,000	32,652,000
Adjustments
Guaranty LIability:
Beginning balance		17,900,000
Adjusted Balance
Guaranty LIability:
Beginning balance		$ 17,950,000