Schedule of Maturities of lease liabilities (Detail) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
2019	[1]	$ 238
2019			$ 474
2020		475	474
2021		475	474
2022		475	474
2023		475	474
Later years		25,640	25,582
Total undiscounted lease payments		27,778	$ 27,952
Less imputed interest		18,916
Ground lease liabilities, net		$ 8,862

[1] Represents the remaining six months of 2019.