Preferred Stock (Narrative) (Details) - USD ($)					1 Months Ended		12 Months Ended
	Feb. 28, 2017	Feb. 27, 2017	Apr. 15, 2016	Mar. 16, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 29, 2012	Dec. 30, 2005
Common Stock [Member]
Class of Stock [Line Items]
Shares issued upon conversion	6,004,957	6,004,957
Shares issued, price per share	$ 10.40	$ 10.40
6.25% Convertible Debt [Member]
Class of Stock [Line Items]
Interest rate				6.25%			6.25%
Principal amount				$ 1,012,000
Real Estate Strategies, L.P. [Member]
Class of Stock [Line Items]
Preferred dividends, cash				$ 1,484,000
Percentage of voting stock				49.00%
Real Estate Strategies, L.P. [Member] | 6.25% Convertible Debt [Member]
Class of Stock [Line Items]
Interest rate				6.25%
Principal amount				$ 1,012,000
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate							8.00%	8.00%
Preferred stock, shares issued											1,521,258
Preferred stock, shares outstanding			803,270						803,270
Preferred stock, redemption price			$ 10.00				$ 10.00
Dividends unpaid and accrued per share			$ 2.084940
Redemption liability			$ 9,707,000
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate							10.00%
Preferred stock, redemption price			$ 25.00				$ 25.00
Dividends unpaid and accrued per share			$ 6.354167
Redeemable preferred stock, shares outstanding			332,500						332,500
Redemption liability			$ 10,425,000
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate						6.25%		6.25%
Preferred stock, value								$ 61,333,000
Preferred dividends, cash							$ 650,000	$ 3,090,000
Preferred stock, shares outstanding				6,245,156				6,245,156
Series D Preferred Stock [Member] | SREP III Flight Investco L.P. [Member]
Class of Stock [Line Items]
Preferred stock, shares issued				3,000,000
Preferred stock, value				$ 30,000,000
Series D Preferred Stock [Member] | Real Estate Strategies, L.P. [Member]
Class of Stock [Line Items]
Preferred stock, shares issued				245,156
Shares issued upon conversion				3,000,000
Series A and B Preferred Stock [Member] | SREP III Flight Investco L.P. [Member]
Class of Stock [Line Items]
Preferred stock, value				$ 20,147,000
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate							6.25%
Preferred stock, shares issued										3,000,000
Percentage of voting stock							34.00%
Series C Preferred Stock [Member] | Real Estate Strategies, L.P. [Member]
Class of Stock [Line Items]
Shares converted				3,000,000
Dividends unpaid and accrued				$ 4,947,000
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate	6.25%				6.25%		6.25%
Preferred stock, value							$ 10,050,000
Shares issued upon conversion		925,000
Preferred dividends, cash							$ 483,000
Preferred stock, shares outstanding							925,000
Shares issued, price per share	$ 13.845
Shares issued upon conversion, amount	$ 9,250,000
Preferred stock, dividend rate increase resulting from failure to pay dividend, with equity offerings	9.50%