Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Deferred:
Federal	$ 3	$ 69	$ 45
Total deferred	3	69	45
Total income tax expense	$ 3	$ 69	$ 45