Stock-Based Compensation - Summary of RSU Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Shares
Granted (in shares)	407	144
Cancelled (in shares)	(59)	(7)	(2)
Equity Incentive Plan2010 [Member] | RSU's
Number of Shares
Non-vested shares at the beginning of the year	148	24	39
Granted (in shares)	407	144
Vested (in shares)	(120)	(12)	(13)
Cancelled (in shares)	(59)	(8)	(2)
Non-vested shares at the end of the period	376	148	24
Weighted Average Grant-Date Fair Value
Weighted average grant date fair value	$ 1.58	$ 8.13	$ 47.17	$ 46.11
Vested (in dollars per share)	5.76	46.06	45.97
Granted (in dollars per share)	0.93	5.30
Cancelled (in dollars per share)	$ 5.04	$ 15.67	$ 46.20