Fair Value of Financial Assets and Liabilities - Derivative Instruments (Valuation Assumptions Used for November 2016 Offering Warrants) (Details) - $ / shares		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Common stock closing price		$ 4.30
November 2016 Warrant Derivative Liability [Member]
Volatility		112.00%	112.00%
Expected term (years)		4 years 7 months 21 days	4 years 10 months 21 days
Risk-free interest rate		1.85%	1.91%
Dividend yield		0.00%	0.00%
Exercise price	[1]	$ 7.50	$ 7.50
Common stock closing price		$ 4.30	$ 4.40

[1] (1) The exercise price of the November 2016 offering warrants will be adjusted downward due to events subsequent to March 31, 2017 (see Note 8).