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Schedule III - Real Estate and Accumulated Depreciation 2 (Detail) - USD ($) $ in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Total gross cost | $ 906,850 | $ 833,203 | $ 782,276 | $ 722,565
Real Estate Held for Sale |  |  |  |
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Real estate held for sale, net | $ 9,027 | $ 8,786 |  |
Building |  |  |  |
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Depreciable life | shorter of the useful life of the asset or 39 years |  |  |
Depreciable life | 39 years |  |  |
Improvements | Minimum |  |  |  |
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Depreciable life | 5 years |  |  |
Improvements | Maximum |  |  |  |
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Depreciable life | 20 years |  |  |

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- Definition Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223 + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Definition Amount, before accumulated depreciation, of real estate investments for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 10 -Section S99 -Paragraph 6 -Subparagraph (SX 210.5-04.(c) Schedule III) -URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28.4) -URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024 + Details
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