Fair Value Measurements and Derivative Instruments (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 01, 2017
Fair Value Measurements And Derivative Instruments [Line Items]
Impairment loss (recovery)	$ 0	$ 0	$ 0	$ 0
Fair value, assets, transfers Level 1 to Level 2	0	0	0	0
Fair value, assets, transfers Level 2 to Level 1	0	0	0	0
Fair value, liabilities, transfers Level 1 to Level 2	0	0	0	0
Fair value, liabilities, transfers Level 2 to Level 3	0	0	0	0
Fair value, assets and liabilities, transfers into/(out of) Level 3	0	0	0	0
Interest Rate Derivatives [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Net gain (loss) on interest rate instruments	$ 124,000	$ (96,000)	$ (664,000)	$ (717,000)
Redemption Rights [Member] \| Series E Preferred Stock [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Number of shares called by redemption					490,250

Asset Impairment Charges (Recovery)

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Fair Value Measurements And Derivative Instruments [Line Items]

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Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of liabilities measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

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- Definition

Amount of gain (loss) included in earnings for the period from the increase (decrease) in fair value of interest rate derivatives not designated as hedging instruments.

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-Section 50
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