Stock Based Compensation (Stock Options) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-Based Compensation
Vesting period	4 years
Stock Options
Share-Based Compensation
Aggregate fair value of options granted	$ 7,000	$ 10,100	$ 6,000
Number of Shares
Outstanding, beginning of the period (in shares)	3,484,298
Granted (in shares)	1,489,384
Exercised (in shares)	(165,803)
Forfeited (in shares)	(664,303)
Canceled (in shares)	(100,949)
Outstanding, end of the period (in shares)	4,042,627	3,484,298
Exercisable (in shares)	2,251,925
Vested or expected to vest (in shares)	3,845,455
Weighted Average Exercise Price Per Share
Outstanding, beginning of the period (in dollars per share)	$ 8.79
Granted (in dollars per share)	8.35
Exercised (in dollars per share)	2.84
Forfeited (in dollars per share)	11.55
Cancelled (in dollars per share)	17.38
Outstanding, end of the period (in dollars per share)	8.20	$ 8.79
Exercisable (in dollars per share)	6.77
Vested or expected to vest (in dollars per share)	$ 8.12
Weighted-Average Remaining Contractual Term (in years)
Outstanding (in years)	7 years 18 days	7 years 7 months 21 days
Exercisable (in years)	5 years 7 months 10 days
Vested or expected to vest (in years)	6 years 11 months 12 days
Aggregate Intrinsic Value
Outstanding, beginning of the period	$ 14,620
Exercised	930
Outstanding, end of the period	4,091	$ 14,620
Exercisable	3,922
Vested or expected to vest	$ 4,084
Weighted-average fair values of options
Weighted average fair value of options granted (in dollars per share)	$ 4.68	$ 8.42	$ 7.59
Fair value assumptions
Weighted-average risk-free interest rate	1.42%	1.69%
Expected dividend yield	0.00%	0.00%
Expected volatility	61.00%	56.00%
Expected terms	6 years	6 years
Stock options
Fair value of stock options vested	$ 4,900	$ 4,000	$ 1,200
Unrecognized compensation cost
Total unrecognized compensation costs related to non-vested stock options	$ 8,800
Remaining weighted-average period that unrecognized compensation costs are expected to be recognized	2 years 6 months 15 days
Performance-based awards
Number of Shares
Granted (in shares)	166,066
Forfeited (in shares)	(20,000)
Outstanding, end of the period (in shares)	146,066
2006 Stock Incentive Plan | Maximum | Stock Options
Share-Based Compensation
Expiration Period	10 years
Vesting period	4 years
2014 Stock Incentive Plan | Stock Options
Share-Based Compensation
Common stock were reserved for issuance	823,529
Percentage of common shares outstanding	4.00%
Shares available for grant	223,397
2014 Stock Incentive Plan | Maximum | Stock Options
Share-Based Compensation
Expiration Period	10 years
Vesting period	4 years