Other Expenses - Schedule of General and Administrative Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Professional services	$ 1,752	$ 1,249	$ 3,414	$ 2,439
Operating and other costs	882	894	2,335	1,249
Subtotal	2,634	2,143	5,749	3,688
Non-cash compensation expenses
Restricted class A common stock earned	8,527	7,629	17,079	15,272
Director stock-based compensation	125	125	250	250
Subtotal	8,652	7,754	17,329	15,522
Total general and administrative expenses	$ 11,286	$ 9,897	$ 23,078	$ 19,210