Common Stock Purchase Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Mar. 07, 2017	Jan. 27, 2017	Mar. 31, 2017	Mar. 31, 2016
Class of Stock [Line Items]
Stock sold price per share (in dollars per share)	$ 0.96
Proceeds from issuance of common stock	$ 10,000		$ 10,000	$ 0
Aspire Capital Fund, LLC [Member]
Class of Stock [Line Items]
Maximum commitment under stock purchase agreement		$ 17,000
Agreement term		30 months
Shares issued during period (in shares)	2,083,333	708,333
Stock sold price per share (in dollars per share)	$ 0.96
Proceeds from issuance of common stock	$ 2,000	$ 2,000