Fair Value Measurements and Derivative Instruments (Narrative) (Details) - USD ($)		1 Months Ended	12 Months Ended
	Feb. 28, 2017	Feb. 29, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 01, 2017
Fair Value Measurements And Derivative Instruments [Line Items]
Adjustment to additional paid in capital, warrant			$ 611,000
Net gain (loss) on interest rate instruments			248,000	$ 190,000	$ 6,680,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset (Liability) Transfers Between Levels			$ 0	$ 0	$ 0
Series C Preferred Stock [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Preferred stock, annual dividend rate		6.25%
Series E Preferred Stock [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Preferred stock, annual dividend rate	6.25%		6.25%
Redemption Rights [Member] | Series E Preferred Stock [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Number of shares called by redemption						490,250
Level 3 [Member] | Redemption Rights [Member] | Series E Preferred Stock [Member]
Fair Value Measurements And Derivative Instruments [Line Items]
Assets fair value	$ 150,000					$ 150,000