Other Expenses - Schedule of General and Administrative Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Professional services	$ 5,163	$ 4,437	$ 3,812
Operating and other costs	3,035	2,938	1,903
Subtotal	8,198	7,375	5,715
Non-cash compensation expenses
Restricted class A common stock earned	30,156	27,654	23,593
Director stock-based compensation	500	500	438
Subtotal	30,656	28,154	24,031
Other expenses			176
Total general and administrative expenses	38,854	35,529	29,922
Manager [Member]
Non-cash compensation expenses
Total general and administrative expenses	$ 38,854	$ 35,529	$ 29,746