Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands, shares in Millions	3 Months Ended							9 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) segment shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Property, Plant and Equipment [Line Items]
Potentially dilutive common shares related to the outstanding preferred stock, stock options, restricted stock units and warrants | shares									10.7	10.0	8.2
Net loss | $	$ 24,887	$ 15,566	$ 16,481	$ 11,833	$ 10,474	$ 10,650	$ 8,955	$ 21,251	$ 78,185	$ 41,912	$ 21,313
Number of operating segments | segment									1
Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets									2 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets									7 years