Fair Value Measurements - Avaliable for Sale (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Available-for-sale securities
Aggregate cost of available-for-sale securities	$ 5,300
Unrealized gain on available-for-sale securities	28,600	$ 27,000
Line of credit
Fair Value of Financial Instruments
Line of credit, gross	29,850,000	18,250,000
Recurring
Available-for-sale securities:
Equity securities	34,000	32,000
Recurring \| Interest rate swap
Financial liabilities:
Derivative financial instruments	8,203,000	4,299,000
Recurring \| Level 1
Available-for-sale securities:
Equity securities	34,000	32,000
Recurring \| Level 2 \| Interest rate swap
Financial liabilities:
Derivative financial instruments	8,203,000	4,299,000
Mortgages payable
Fair Value of Financial Instruments
Estimated fair value of mortgages payable	336,424,000	346,614,000
Carrying value of mortgage loans	325,186,000	334,428,000
Excess of fair value over carrying value	$ 11,238,000	$ 12,186,000
Blended or estimated market interest rate (as a percent)	4.01%	4.07%
Weighted average remaining term of the mortgages	9 years 8 months 12 days	8 years 10 months 24 days

Represents the amount of difference between the fair value and carrying value.

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- Definition

Represents the weighted average remaining term of the mortgages based on which the market interest rate is assumed.

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No definition available.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit before netting of deferred finance costs, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations before netting of deferred finance costs (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

No definition available.

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- Definition

This item represents the cost of equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of equity securities categorized neither as held-to-maturity nor as trading.

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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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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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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