Fair Value Measurements (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Unrealized gain recognized	$ 453,412	$ (32,119)
Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	32,718,000		$ 35,834,000
Warrant liabilities	(74,000)		(527,000)
Level I [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	32,718,000		35,834,000
Warrant liabilities	0		0
Level II [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	0		0
Warrant liabilities	0		0
Level III [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Unrealized gain recognized	453,000
Level III [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	0		0
Warrant liabilities	$ (74,000)		$ (527,000)