Annual report pursuant to Section 13 and 15(d)

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

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Schedule III - Real Estate and Accumulated Depreciation - Change in Balance of Real Estate (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]      
Balance at beginning of period $ 906,850,000 $ 833,203,000  
Additions:      
Acquisitions during period 53,432,000 100,103,000 $ 52,719,000
Improvements 4,824,000 10,473,000 10,362,000
Deductions:      
Dispositions during period (15,284,000) (30,094,000) (10,138,000)
Impairments during period 0 (6,835,000) (2,016,000)
Balance at end of period $ 949,822,000 $ 906,850,000 $ 833,203,000