Stock-Based Compensation - Stock awards activity (Details) - 2010 Equity Incentive Plan - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, outstanding at December 31, 2017, shares	2,490,465
Options, granted, shares	0
Options, exercised, shares	(5,042)
Options, cancelled, shares	(33,728)
Options, outstanding at June 30, 2018, shares	2,451,695
Options, vested and expected to vest, shares	2,446,937
Options, exercisable, shares	2,353,368
Options, outstanding at December 31, 2017, weighted average exercise price	$ 9.58		$ 9.58	$ 9.59
Options, granted, weighted average exercise price	0.00
Options, exercised, weighted average exercise price	4.33
Options, cancelled, weighted average exercise price	11.48
Options, outstanding at June 30, 2018, weighted average exercise price	9.58
Options, vested and expected to vest, weighted average exercise price	9.57
Options, exercisable, weighted average exercise price	$ 9.44
Options, exercisable, weighted average remaining contractual term	4 years 7 months 6 days
Options, exercisable, intrinsic value			$ 945,000
Options, outstanding, weighted average remaining contractual term	4 years 8 months 5 days
Options, outstanding, intrinsic value			948,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity award other than options, unvested at December 31, 2017, shares	2,073,440
Equity award other than options, granted, shares	1,677,126
Equity award other than options, vested, shares	(548,089)
Equity award other than options, cancelled, shares	(119,547)
Equity award other than options, unvested at June 30, 2018, shares	3,082,930
Equity award other than options, unvested, weighted average grant date fair value	$ 9.14
Equity award other than options, granted, weighted average grant date fair value	4.45
Equity award other than options, vested, weighted average grant date fair value	9.74
Equity award other than options, cancelled, weighted average grant date fair value	9.02
Equity award other than options, unvested, weighted average grant date fair value	$ 6.49
Equity award other than options, vested in period, fair value	$ 2,929,115	$ 3,235,000
Nonvested award, compensation cost not yet recognized			14,079,000
Nonvested award, compensation cost not yet recognized, weighted average period for recognition	2 years 8 months 21 days
Market-based share unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity award other than options, unvested at December 31, 2017, shares	233,743
Equity award other than options, granted, shares	320,000
Equity award other than options, unvested at June 30, 2018, shares	553,743
Equity award other than options, unvested, weighted average grant date fair value	$ 10.88
Equity award other than options, granted, weighted average grant date fair value	7.19	$ 13.82
Equity award other than options, unvested, weighted average grant date fair value	$ 8.75
Nonvested award, compensation cost not yet recognized			$ 1,902,000
Nonvested award, compensation cost not yet recognized, weighted average period for recognition	1 year 9 months 12 days