Preferred Stock (Narrative) (Details) - USD ($)				9 Months Ended		12 Months Ended
	Feb. 28, 2017	Apr. 15, 2016	Mar. 16, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Common Stock [Member]
Class of Stock [Line Items]
Shares issued upon conversion	6,004,957
Shares issued, price per share	$ 10.40
Real Estate Strategies, L.P. [Member] | Promissory Note [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%
Preferred stock, shares outstanding		803,270
Preferred stock, redemption price		$ 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, shares outstanding		332,500
Dividends unpaid and accrued per share		$ 6.354167
Preferred stock, temporary equity, redemption price		$ 25.00
Redemption liability		$ 10,425,000
Series A and B Preferred Stock [Member] | SREP III Flight Investco L.P. [Member]
Class of Stock [Line Items]
Escrow deposit for effecting redemtion			$ 20,147,000
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate			6.25%
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
Preferred dividends, cash			$ 1,484,000
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate						6.25%
Preferred stock, value						$ 61,333,000
Preferred dividends, cash				$ 650,000	$ 2,115,000
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]
Shares issued upon conversion			3,000,000
Preferred dividends, stock			$ 245,156
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate	6.25%			6.25%
Preferred stock, value	$ 9,900,000			$ 10,050,000
Preferred dividends, cash				$ 339,000
Preferred stock, shares outstanding	925,000			925,000
Redeemable preferred stock, shares issued	925,000
Maximum [Member] | Real Estate Strategies, L.P. [Member]
Class of Stock [Line Items]
Percentage of voting stock			49.00%