STOCKHOLDERS' EQUTIY AND SHARE-BASED COMPENSATION EXPENSE - Summary of outstanding and exercisable options (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Options Outstanding (in shares) | shares	3,405
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	3 years 7 months 10 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 6.46
Number of Option Exercisable (in shares) | shares	2,091
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 5.65
Range $2.70 - 3.91 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range Exercise Price, Lower Range Limit (in dollars per share)	2.93
Range of Exercise Price, Upper Range Limit (in dollars per share)	$ 3.91
Number of Options Outstanding (in shares) | shares	904
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	3 years 6 months 11 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 3.72
Number of Option Exercisable (in shares) | shares	574
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 3.68
Range $4.16 - 5.29 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range Exercise Price, Lower Range Limit (in dollars per share)	4.16
Range of Exercise Price, Upper Range Limit (in dollars per share)	$ 5.07
Number of Options Outstanding (in shares) | shares	709
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	2 years 5 months 5 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 4.45
Number of Option Exercisable (in shares) | shares	642
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 4.46
Range $5.31 - 6.71 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range Exercise Price, Lower Range Limit (in dollars per share)	5.21
Range of Exercise Price, Upper Range Limit (in dollars per share)	$ 7.55
Number of Options Outstanding (in shares) | shares	857
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	3 years 4 months 13 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 6.48
Number of Option Exercisable (in shares) | shares	573
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 6.22
Range $7.05 - 10.29 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range Exercise Price, Lower Range Limit (in dollars per share)	7.62
Range of Exercise Price, Upper Range Limit (in dollars per share)	$ 11.88
Number of Options Outstanding (in shares) | shares	834
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	4 years 9 months 29 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 9.62
Number of Option Exercisable (in shares) | shares	266
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 8.27
Range $10.52 - 37.22 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range Exercise Price, Lower Range Limit (in dollars per share)	12.24
Range of Exercise Price, Upper Range Limit (in dollars per share)	$ 36.16
Number of Options Outstanding (in shares) | shares	101
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	4 years 5 months 8 days
Option Outstanding, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 18.56
Number of Option Exercisable (in shares) | shares	36
Option Exercisable, Weighted-Average Exercise Price Per Share (in dollars per share)	$ 29.96