Stock-Based Compensation - Employee Stock Option and Incentive Plan Activity (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares
Options Outstanding at beginning of the period (in shares)	723,747
Granted (in shares)	338,517
Exercised (in shares)	(6,967)
Canceled (in shares)	(189,165)
Options Outstanding at the end of the period (in shares)	866,132	723,747
Options Vested and Expected to Vest at the end of the period (in shares)	846,352
Options Exercisable at the end of the period (in shares)	426,612
Shares Available for Grant Under the 2008 Plan	356,913
Weighted Average Exercise Price Per Share
Options Outstanding at beginning of the period (in dollars per share)	$ 141.00
Granted (in dollars per share)	9.11
Exercised (in dollars per share)	42.00
Canceled (in dollars per share)	125.38
Options Outstanding at the end of the period (in dollars per share)	93.70	$ 141.00
Options Vested and Expected to Vest at the end of the period (in dollars per share)	95.47
Options Exercisable at the end of the period (in dollars per share)	$ 162.83
Weighted Average Remaining Contractual Term (In Years)
Options Outstanding at the end of the period	7 years 1 month 6 days	6 years 1 month 6 days
Options Vested and Expected to Vest at the end of the period	7 years
Options Exercisable at the end of the period	5 years 1 month 6 days