Financial Guarantee Liability - Summary of Changes on Estimated Liability Under Guarantee Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Guaranty LIability:
Beginning balance	$ 15	$ 32
Reversal of provision		(17)
Provision for expected credit losses	11,631
Ending balance	29,581	15
Cumulative Effect, Period of Adoption, Adjustment
Guaranty LIability:
Beginning balance	$ 17,935
Ending balance		$ 17,935