STOCK-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Stock-based compensation
Stock-based compensation expense	$ 6,100	$ 4,500
Valuation assumptions
Risk-free interest rates (as a percent)	2.13%		2.13%
Expected term			6 years 7 months 2 days
Expected volatility (as a percent)	62.90%		62.90%
Dividend yield (as a percent)			0.00%
Weighted average fair value per share of options granted during the period (in dollars per share)			$ 13.20
Additional disclosures
Market price (in dollars per share)	$ 35.37		$ 35.37
Total intrinsic value of options exercised			$ 2,600	$ 4,600
Weighted Average Grant Date Fair Value
Unrecognized compensation cost	$ 49,700		$ 49,700
Weighted average period for recognition of unrecognized compensation cost			2 years 8 months 12 days
Share based compensation expense	$ 6,100	$ 4,500
Stock Options
Valuation assumptions
Risk-free interest rates, minimum (as a percent)		1.48%		1.48%
Risk-free interest rates, maximum (as a percent)		1.69%		1.69%
Expected term	6 years 7 months 2 days
Expected volatility, minimum (as a percent)		58.90%		58.90%
Expected volatility, maximum (as a percent)		59.40%		59.40%
Dividend yield (as a percent)	0.00%	0.00%		0.00%
Weighted average fair value per share of options granted during the period (in dollars per share)	$ 13.20	$ 3.17		$ 3.17
Shares
Outstanding at the beginning of the period (in shares)			3,505,481
Granted (in shares)			125,978
Exercised (in shares)			(108,205)
Forfeited (in shares)			(10,035)
Outstanding at the end of the period (in shares)	3,513,219		3,513,219		3,505,481
Exercisable at the end of the period (in shares)	2,551,473		2,551,473
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)			$ 7.00
Granted (in dollars per share)			21.68
Exercised (in dollars per share)			7.16
Forfeited (in dollars per share)			14.48
Outstanding at the end of the period (in dollars per share)	$ 7.50		7.50		$ 7.00
Exercisable at the end of the period (in dollars per share)	$ 6.17		$ 6.17
Weighted Average Remaining Contractual Term
Outstanding at the end of the period			5 years 2 months 12 days		5 years 6 months
Exercisable at the end of the period			4 years
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 97,900		$ 97,900
Exercisable at the end of the period	$ 74,503		$ 74,503
Stock Options | Minimum
Valuation assumptions
Expected term		6 years 3 months		6 years 3 months
Stock Options | Maximum
Valuation assumptions
Expected term		6 years 8 months 27 days		6 years 8 months 27 days
Market Measure-Based Shares
Valuation assumptions
Risk-free interest rates, minimum (as a percent)				0.91%
Risk-free interest rates (as a percent)		0.91%
Expected term		2 years 10 months 2 days		2 years 10 months 2 days
Expected volatility (as a percent)		68.30%
Expected volatility, minimum (as a percent)				68.30%
Dividend yield (as a percent)		0.00%		0.00%
Weighted average fair value per share of stock purchase rights granted during the period (in dollars per share)		$ 2.32		$ 2.32
Weighted Average Grant Date Fair Value
Granted (in dollars per share)		$ 2.32		$ 2.32
Employee Stock
Valuation assumptions
Risk-free interest rates, minimum (as a percent)	0.98%	0.41%	0.98%	0.41%
Risk-free interest rates, maximum (as a percent)	1.28%	0.80%	1.28%	0.80%
Expected volatility, minimum (as a percent)	66.40%	70.10%	66.40%	70.10%
Expected volatility, maximum (as a percent)	85.50%	92.70%	85.50%	92.70%
Dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%
Weighted average fair value per share of stock purchase rights granted during the period (in dollars per share)	$ 13.05	$ 3.08	$ 13.05	$ 3.08
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 13.05	$ 3.08	$ 13.05	$ 3.08
Employee Stock | Minimum
Valuation assumptions
Expected term	6 months	6 months	6 months	6 months
Employee Stock | Maximum
Valuation assumptions
Expected term	2 years	2 years	2 years	2 years
Restricted Stock Awards And Restricted Stock Units RSU
Valuation assumptions
Weighted average fair value per share of stock purchase rights granted during the period (in dollars per share)			$ 23.26
Restricted Shares
Outstanding at the beginning of the period (in shares)			5,601,316
Granted (in shares)			915,492
Released (in shares)			(839,252)
Forfeited (in shares)			(253,133)
Outstanding at the end of the period (in shares)	5,424,423		5,424,423		5,601,316
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)			$ 9.19
Granted (in dollars per share)			23.26
Released (in dollars per share)			12.38
Forfeited (in dollars per share)			18.79
Outstanding at the end of the period (in dollars per share)	$ 10.80		$ 10.80		$ 9.19