Fair Value Measurements And Derivative Instruments (Narrative) (Details) - USD ($)		1 Months Ended	12 Months Ended
	Feb. 28, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	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			190,000	$ 6,680,000	$ 11,578,000
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%	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