STOCK-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Stock-based compensation
Stock-based compensation expense	$ 6,100	$ 3,600
Forfeiture rate (as a percent)	3.48%	4.99%
Additional disclosures
Market price (in dollars per share)	$ 6.74
Total intrinsic value of options exercised	$ 2,100	$ 400
Weighted Average Grant Date Fair Value
Unrecognized compensation cost	$ 52,600
Weighted average period for recognition of unrecognized compensation cost	3 years
Share based compensation expense	$ 6,100	$ 3,600
Stock Options
Valuation assumptions
Risk-free interest rates, minimum (as a percent)	1.48%	1.50%
Risk-free interest rates, maximum (as a percent)	1.69%	1.92%
Expected volatility, minimum (as a percent)	58.90%	67.10%
Expected volatility, maximum (as a percent)	59.40%	73.20%
Weighted average fair value per share of options granted during the period (in dollars per share)	$ 3.17	$ 15.81
Shares
Outstanding at the beginning of the period (in shares)	4,936,594
Granted (in shares)	883,889
Exercised (in shares)	(332,924)
Forfeited (in shares)	(12,150)
Outstanding at the end of the period (in shares)	5,475,409		4,936,594
Exercisable at the end of the period (in shares)	4,175,037
Vested and expected to vest at the end of the period (in shares)	5,309,942
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 4.80
Granted (in dollars per share)	5.48
Exercised (in dollars per share)	0.87
Forfeited (in dollars per share)	16.52
Outstanding at the end of the period (in dollars per share)	5.10		$ 4.80
Exercisable at the end of the period (in dollars per share)	3.66
Vested and expected to vest at the end of the period (in dollars per share)	$ 5.05
Weighted Average Remaining Contractual Term
Outstanding at the end of the period	5 years 1 month 6 days		4 years 6 months
Exercisable at the end of the period	3 years 10 months 24 days
Vested and expected to vest at the end of the period	5 years 1 month 6 days
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 18,052
Exercisable at the end of the period	16,974
Vested and expected to vest at the end of the period	$ 17,964
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 7 months 6 days
Market Measure-Based Shares
Valuation assumptions
Risk-free interest rates, minimum (as a percent)	0.91%
Expected term	2 years 10 months 2 days
Expected volatility (as a percent)	68.30%
Weighted average fair value per share of stock purchase rights granted during the period (in dollars per share)	$ 2.32
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	2.32
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)	$ 4.37
Restricted Shares
Outstanding at the beginning of the period (in shares)	3,444,694
Granted (in shares)	3,244,764
Released (in shares)	(422,379)
Forfeited (in shares)	(64,840)
Outstanding at the end of the period (in shares)	6,202,239		3,444,694
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 14.19
Granted (in dollars per share)	4.37
Released (in dollars per share)	16.73
Forfeited (in dollars per share)	20.18
Outstanding at the end of the period (in dollars per share)	$ 8.61		$ 14.19