Leases - Schedule of Operating Lease Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee Lease Description [Line Items]
Total lease costs	$ 5,343	$ 6,332
Operating and Maintenance [Member]
Lessee Lease Description [Line Items]
Total lease costs	2,716	3,495
General and Administrative [Member]
Lessee Lease Description [Line Items]
Total lease costs	$ 2,627	$ 2,837