Stock Compensation (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 25, 2013
Number of Options
Outstanding at the beginning of period (in shares)	1,401,101
Granted (in shares)	561,500
Forfeited or expired (vested and unvested) (in shares)	(125,052)
Exercised (in shares)	(107,963)
Outstanding at the end of the period (in shares)	1,729,586	1,401,101
Weighted-Average Price Per Share
Outstanding at the beginning of period (in dollars per share)	$ 9.59
Granted (in dollars per share)	$ 15.03
Forfeited or expired (vested and unvested) (in dollars per share)	$ 12.97
Exercised (in dollars per share)	$ 4.38
Outstanding at the end of the period (in dollars per share)	$ 11.44	$ 9.59
Weighted-Average Remaining Contractual Term (Years)
Outstanding at the end of the period	8 years 5 months 5 days	8 years 11 months 12 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 50,155,000	$ 7,755,000
Information about the stock option plan
Number of Options, vested and expected to vest (in shares)	1,671,313
Number of Options, exercisable (in shares)	752,397
Weighted-Average Price Per Share, vested and expected to vest (in dollars per share)	$ 11.37
Weighted-Average Price Per Share, exercisable (in dollars per share)	$ 6.61
Weighted-Average Remaining Contractual Term, vested and expected to vest	8 years 4 months 28 days
Weighted-Average Remaining Contractual Term, exercisable	7 years 6 months 29 days
Aggregate Intrinsic Value, vested and expected to vest (in dollars)	48,588,000
Aggregate Intrinsic Value, exercisable (in dollars)	25,452,000
Total intrinsic value of stock options exercised	1,400,000	200,000	100,000
Additional disclosures
Unrecognized compensation cost (in dollars)	9,300,000
Weighted-average period over which remaining unrecognized compensation cost will be recognized	2 years 10 months 24 days
Weighted-average grant-date fair value (in dollars per share)	$ 10.15	$ 7.14	$ 1.33
Stock-based compensation expense	$ 3,700,000	$ 1,200,000	$ 100,000
Assumptions used to compute the share-based compensation costs for stock options granted to employees and non-employees
Risk-free interest rate (as a percent)	1.81%	1.45%	0.85%
Weighted-average expected life of options (years)	6 years 3 months 26 days	6 years 3 months 4 days	6 years 3 months
Volatility (as a percent)	75.00%	74.00%	80.00%
2013 Stock Option and Incentive Plan
Stock compensation
Shares reserved and approved for issuance				1,100,000
Shares reserved under previous plan and subsequently transferred to new plan				54,129
Percentage of increase in the number of shares reserved and available for issuance				2.50%
2008 Incentive Stock Option and Restricted Stock Plan
Stock compensation
Shares reserved under previous plan and subsequently transferred to new plan				54,129
Expiration period	10 years
Period from cessation of employment within which options expire if not exercised	90 days
Grant period of stock awards	10 years
Purchase price expressed as a percentage of fair value of shares on the date of grant	100.00%
Vesting percentage on the first anniversary of the option grant	25.00%
Period for which remainder of grant amount will vest on the first day of each calendar quarter	3 years