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Commitments and Contingencies - Additional Information (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($) Property ApartmentUnit | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Accrual for environmental loss contingencies | $ 2.8 |  |
Number of properties with environmental reserves | Property | 2 |  |
Loss contingency accrual | $ 0.9 |  |
Projects in various stages of development | Property | 4 |  |
Units in various stages of development | ApartmentUnit | 892 |  |
Consolidated project under development commitment fund | $ 136.1 |  |
Various stages of development with estimated completion dates ranging through December 31, 2019 | Dec. 31, 2019 |  |
Total operating lease payments | $ 26.6 | $ 26.2 | $ 24.5
Compensation expense, recognized | $ 0.4 | $ 0.3 | $ 0.4
Partially Owned Properties – Unconsolidated |  |  |
Number of unconsolidated projects | Property | 2 |  |

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- Definition Represents the company's remaining funding obligation (i.e. total project costs less book value) for consolidated projects that are under development. + References No definition available. + Details
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- Definition Total number of open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. These projects are consolidated. + References No definition available. + Details
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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
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