Net Income (Loss) Per Share (Computation of Basic and Diluted Net Loss Per Share) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Abstract]
Net loss	$ (9,500,000)	$ (2,375,000)	$ (3,851,000)	$ (3,112,000)	$ (2,231,000)	$ 5,439,000	$ 10,769,000	$ (14,493,000)	$ (18,838,000)	$ (516,000)
Excess of fair value of consideration transferred on conversion of Series B Preferred Stock		(1,214,000)	(2,366,000)						(3,580,000)
Accretion of Series B redeemable convertible preferred stock			(133,000)	(1,725,000)	(949,000)	(7,163,000)	(1,828,000)	(338,000)	(1,858,000)	(10,278,000)
Net loss attributable to common stockholders	$ (9,500,000)	$ (3,589,000)	$ (6,350,000)	$ (4,837,000)	$ (3,180,000)	$ (1,724,000)	$ 8,941,000	$ (14,831,000)	$ (24,276,000)	$ (10,794,000)
Weighted average number of shares of common stock outstanding - basic & diluted									9,838,455	5,411,204
Net loss per share of common stock - basic & diluted									$ (2.47)	$ (1.99)