Warrants to Acquire Shares of Common Stock (Schedule of Warrant Activity) (Details)	3 Months Ended
	Mar. 31, 2018 shares
Class of Warrant or Right, Outstanding [Roll Forward]
Warrants outstanding , Beginning balance (in shares)	963,000
Granted (in shares)	774,000
Canceled (in shares)	(501,000)
Warrants outstanding , Ending balance (in shares)	1,236,000
Series A Convertible Preferred
Class of Warrant or Right, Outstanding [Roll Forward]
Warrants outstanding , Beginning balance (in shares)	0
Granted (in shares)	774,000
Canceled (in shares)	0
Warrants outstanding , Ending balance (in shares)	774,000
2017 Equilibria
Class of Warrant or Right, Outstanding [Roll Forward]
Warrants outstanding , Beginning balance (in shares)	316,000
Granted (in shares)	0
Canceled (in shares)	0
Warrants outstanding , Ending balance (in shares)	316,000
Galena February 2017
Class of Warrant or Right, Outstanding [Roll Forward]
Warrants outstanding , Beginning balance (in shares)	567,000
Granted (in shares)	0
Canceled (in shares)	(501,000)
Warrants outstanding , Ending balance (in shares)	66,000
Galena Other
Class of Warrant or Right, Outstanding [Roll Forward]
Warrants outstanding , Beginning balance (in shares)	80,000
Granted (in shares)	0
Canceled (in shares)	0
Warrants outstanding , Ending balance (in shares)	80,000