Schedule II Valuation and qualifying accounts: (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts - Tenant rent receivables
Movement in valuation and qualifying accounts
Balance at beginning of year	$ 325,000	$ 50,000	$ 1,300,000
Additions (Decreases) charged to costs and expenses	(106,000)	394,000	(13,000)
Deductions	(89,000)	(119,000)	(1,237,000)
Balance at end of year	130,000	325,000	50,000
Allowance for doubtful accounts - Straight-line rent receivable
Movement in valuation and qualifying accounts
Balance at beginning of year	162,000	135,000	135,000
Additions (Decreases) charged to costs and expenses	(112,000)	27,000	48,000
Deductions	(112,000)		(48,000)
Balance at end of year	$ 50,000	$ 162,000	$ 135,000

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 09
-Article 12

+ Details

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- Definition

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- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

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