Stockholders' Equity and Stock-based Compensation - Stock Options Outstanding Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Beginning balance (in shares)	847,635	560,797	599,069
Options granted (in shares)	156,000
Exercised (in shares)	(15,000)
Options cancelled (in shares)	(50,682)
Options forfeited (in shares)	(47,612)
Ending balance (in shares)	890,341	847,635	560,797
Options exercisable and vested (in shares)	435,278
Weighted Average Exercise Price
Beginning balance (usd per share)	$ 46.21
Options granted (usd per share)	13.15
Options exercised (usd per share)	3.10
Options cancelled (usd per share)	7.32
Options forfeited (usd per share)	180.52
Ending balance (usd per share)	36.17	$ 46.21
Options exercisable and vested (usd per share)	63.25
Additional Disclosures
Weighted average grant date fair value for stock option awards (usd per share)	$ 8.10	$ 2.04	$ 16.65
Weighted average remaining contractual life, outstanding	6 years 4 months 24 days	6 years 1 month 6 days
Weighted Average Remaining Contractual Life, Options exercisable and vested	5 years 4 months 24 days
Aggregate intrinsic value, outstanding	$ 6,774	$ 1,175
Aggregate Intrinsic Value, Options exercisable and vested	$ 1,436