Leases - Summary of Fixed and Variable Components of Operating Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Fixed ground rent expense	$ 390	$ 185	$ 1,108	$ 321
Variable ground rent expense		26	21	56
Total cash portion of ground rent expense	390	211	1,129	377
Non-cash ground rent expense	1,091	98	3,275	256
Total operating lease costs	$ 1,481	$ 309	$ 4,404	$ 633