SHAREHOLDER'S EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
ESPP [Line items]
Other current liabilities	$ 771						$ 771		$ 1,279
Other long term liabilities	988						988		1,041
Total Dividend Equivalent Liability	$ 1,759						$ 1,759		$ 2,320
Espp Shares Market Value	85.00%						85.00%
Employee stock purchase plan, authorized shares	1,000,000.0						1,000,000.0
ESPP Share Discount	15.00%						15.00%
Number of shares purchased				0	0	0
Non cash compensation expense recognized	$ 2,571	$ 2,982					$ 8,028	$ 9,036
Stock Repurchase Prgram Authorized Amount	$ 100,000						$ 100,000
Number of Shares Authorized to be Repurchased	0						0
Common stock repurchase VALUE	$ 18,340		$ 19,379
Common Class A [Member]
ESPP [Line items]
Number of shares repurchased	5,000,000		1,833,200
Common stock repurchase VALUE	$ 50		$ 18
ESPP [Member]
ESPP [Line items]
Number of shares purchased							260,000	150,000
Non cash compensation expense recognized							$ 182	$ 185
Share repurchase program 2017 [Member]
ESPP [Line items]
Common stock repurchase VALUE							$ 18,300
Share repurchase program 2017 [Member] | Common Class A [Member]
ESPP [Line items]
Number of shares repurchased							5,000,000.0
Average repurchase price per share	$ 3.67						$ 3.67