Schedule of Maturities of lease liabilities (Detail) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
2019	[1]	$ 120
2019			$ 474
2020		480	474
2021		480	474
2022		480	474
2023		480	474
Later years		25,921	25,582
Total undiscounted lease payments		27,961	$ 27,952
Less imputed interest		19,010
Ground lease liabilities, net		$ 8,951

[1] Represents the remaining three months of 2019.