Common Stock (Narrative) (Details)							12 Months Ended
	Mar. 29, 2017 USD ($) $ / shares shares	Mar. 15, 2017 USD ($) shares	Feb. 28, 2017 $ / shares shares	Feb. 27, 2017 $ / shares shares	Jan. 24, 2017 USD ($) $ / shares shares	Mar. 11, 2015 $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) shares	Sep. 20, 2017 USD ($)
Class of Stock [Line Items]
Warrant issuance costs | $							$ 289,000	$ 12,000	$ 58,000
Reverse stock split, conversion ratio		0.1538
Reverse stock split, fractional shares issued		0
Reverse stock split, shares settled in cash		73
Reverse stock split, shares settled in cash, amount | $		$ 1,000					1,000
Proceeds from common stock issued | $							47,468,000		$ 346,000
Issuance costs | $							$ 1,210,000
Underwritten Public Offering [Member]
Class of Stock [Line Items]
Shares issued, price per share | $ / shares	$ 10.50
Issuance of common stock, shares	4,772,500
Proceeds from common stock issued | $	$ 45,850,000
ATM Program [Member]
Class of Stock [Line Items]
Shares issued, price per share | $ / shares							$ 10.15
Issuance of common stock, shares							169,004
Proceeds from common stock issued | $							$ 1,715,000
Equity distribution agreement, commission fee, percent							2.00%
Net proceeds from common stock issue | $							$ 1,619,000
Maximum [Member] | ATM Program [Member]
Class of Stock [Line Items]
Equity distribution agreement, aggregate price of shares available for sale | $										$ 50,000,000
Minimum [Member] | ATM Program [Member]
Class of Stock [Line Items]
Public float required to sell shares of common stock | $										$ 75,000,000
Pursuant To Full Exercise Of An Option To Purchase Additional Shares Of Common Stock Granted To Underwriters [Member] | Underwritten Public Offering [Member]
Class of Stock [Line Items]
Issuance of common stock, shares	622,500
New Warrants [Member]
Class of Stock [Line Items]
Shares issued upon conversion					23,160
Common stock warrants, exercise price | $ / shares					$ 0.0065
Warrant expiration					Jan. 24, 2019
Warrant issuance costs | $					$ 289,000
Warrants [Member] | Executive Officer [Member]
Class of Stock [Line Items]
Stock issued by exercise of warrant or right						35,060
Common stock warrants, exercise price | $ / shares						$ 9.88
Real Estate Strategies, L.P. [Member] | Warrants [Member]
Class of Stock [Line Items]
Shares converted					576,923
Common Stock [Member]
Class of Stock [Line Items]
Shares issued upon conversion			6,004,957	6,004,957
Number of shares called by warrant					23,160
Shares issued, price per share | $ / shares			$ 10.40	$ 10.40
Issuance of common stock, shares							4,972,000		35,000