Annual report pursuant to Section 13 and 15(d)

Schedule III - Real Estate and Accumulated Depreciation - Schedule of Change in Balance of Accumulated Depreciation (Detail)

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Schedule III - Real Estate and Accumulated Depreciation - Schedule of Change in Balance of Accumulated Depreciation (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, beginning of period $ 11,066 $ 6,634 $ 4,431
Additions during period 6,180 4,446 2,203
Dispositions during period (589) (14) 0
Balance, end of period $ 16,657 $ 11,066 $ 6,634