Debt - Mortgages Payable (Details) - USD ($)	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total	$ 739,200,000
Long-term Debt, Total	739,166,000
Mortgages [Member]
Debt Instrument [Line Items]
Total	60,166,000	$ 61,519,000
Unamortized debt issuance costs	(496,000)	(593,000)
Long-term Debt, Total	59,670,000	60,926,000
Notes Payable Due October 2019 3.32 percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 21,500,000	21,500,000
Debt Instrument, Interest Rate, Stated Percentage	3.32%
Notes Payable Due January 2020 6.90 Percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 1,053,000	1,922,000
Debt Instrument, Periodic Payment, Principal	$ 153,838
Debt Instrument, Interest Rate, Stated Percentage	6.90%
Notes Payable Due February 2020 6.24 Percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 2,824,000	2,872,000
Debt Instrument, Periodic Payment, Principal	23,004
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid	$ 2,781,819
Debt Instrument, Interest Rate, Stated Percentage	6.24%
Notes Payable Due January 2023 3.60 Percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 23,640,000	23,640,000
Debt Instrument, Interest Rate, Stated Percentage	3.60%
Notes Payable Due September 2023 5.01 Percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 4,870,000	4,959,000
Debt Instrument, Periodic Payment, Principal	35,673
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid	$ 4,034,627
Debt Instrument, Interest Rate, Stated Percentage	5.01%
Notes Payable Due July 2026 6.27 Percent [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Total	$ 6,279,000	$ 6,626,000
Debt Instrument, Periodic Payment, Principal	$ 91,675
Debt Instrument, Interest Rate, Stated Percentage	6.27%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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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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Amount of the required periodic payments applied to principal.

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Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

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