Real Estate Properties - Income Statement Information for Disposal of Property (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations	$ 173	$ (589)	$ (525)
Discontinued Operations, Held-for-sale \| Discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income	17	68	114
Real estate taxes	(88)	(97)	(92)
Utility expenses	(97)	(146)	(161)
Other operating expenses	(202)	(300)	(272)
General and administrative	(76)	(114)	(114)
Increase in carrying value of property included in discontinued operations	619	0	0
Income (loss) from discontinued operations	$ 173	$ (589)	$ (525)

Disposal Group, Including Discontinued Operation, Gain on Sale of Property

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Amount of other operating expenses attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of real estate taxes attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of utility expenses attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of general and administrative expense attributable to disposal group, including, but not limited to, discontinued operation.

+ References

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Amount of rental income attributable to disposal group, including, but not limited to, discontinued operation.

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Amount after tax of income (loss) from a discontinued operation attributable to the parent. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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