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Real Estate Dispositions, Held for Sale and Impairment Charges - Components of Income from Real Estate and Related Assets Held for Sale Additional Information (Detail) $ in Thousands |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
May 16, 2016 USD ($) | Dec. 31, 2016 property | Sep. 30, 2016 USD ($) property | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) property | Sep. 30, 2015 USD ($)
Real Estate Properties [Line Items] |  |  |  |  |  |
Impairment charge |  |  | $ 1,786 | $ 622 | $ 2,016 | $ 622
Number of real estate properties, held for sale | property |  |  | 5 |  | 5 |
Rock Falls, Illinois and Angola, Indiana [Member] |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |
Impairment charge | $ 20 |  |  |  | $ 20 |
Dayton Ohio [Member] |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |
Impairment charge | $ 40 |  |  |  | $ 40 | $ 600
Scenario, Forecast [Member] |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |
Number of properties sold | property |  | 4 |  |  |  |

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- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2420-110228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 + Details
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