Net Loss per Common Share (Basic and Diluted Income (Loss) Per Share) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic and diluted net loss per common share calculation:
Net loss	$ (6,461,000)	$ (3,851,000)	$ (9,707,000)	$ (6,963,000)
Excess of fair value of consideration transferred on conversion of Series B redeemable convertible preferred stock		(2,366,000)		(2,366,000)
Accretion of Series B redeemable convertible preferred stock		(133,000)		(1,858,000)
Net loss attributable to common stockholders - basic	(6,461,000)	(6,350,000)	(9,707,000)	(11,187,000)
Net loss attributable to common stockholders - diluted	$ (8,041,000)	$ (6,350,000)	$ (11,287,000)	$ (11,187,000)
Weighted average number of shares of common stock outstanding - basic	5,350,930	874,062	3,514,181	731,206
Net loss per share of common stock - basic	$ (1.21)	$ (7.26)	$ (2.76)	$ (15.30)
Weighted average number of shares of common stock outstanding - diluted	5,519,895	876,806	3,652,501	732,578
Net loss per share of common stock - diluted	$ (1.46)	$ (7.82)	$ (3.09)	$ (15.96)
November 2016 Warrant Derivative Liability [Member]
Basic and diluted net loss per common share calculation:
Changes in estimated fair value of warrants	$ (1,580,000)		$ (1,580,000)