Stockholder's Equity, Stock-Based Compensation Expense and Repurchase Plan - Narrative (Details) - USD ($)	9 Months Ended		23 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 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	782,739	877,569	782,739
Number of shares of restricted stock and shares reserved for restricted stock units outstanding	163,184	293,340	163,184
Stock-based compensation expense	$ 1,694,000	$ 2,512,000
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