Stockholder's Equity, Stock-Based Compensation Expense and Repurchase Plan - Narrative (Details) - USD ($)	6 Months Ended		20 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 22, 2016	Nov. 04, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Maximum number of shares available for sale through the ATM Program				20,000,000
Number of shares issued or committed for issuance under outstanding stock options	838,582	900,623	838,582
Number of shares of restricted stock and shares reserved for restricted stock units outstanding	187,675	293,709	187,675
Stock-based compensation expense	$ 1,169,000	$ 1,610,000
Stock repurchase amount, authorized amount					$ 25,000,000
Shares repurchased, value			$ 3,000,000
Number of shares repurchased			451,792
Repurchased shares, average price per share (usd per share)			$ 6.41