SHAREHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Feb. 20, 2019	Feb. 21, 2018	May 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Annual interest rate on convertible senior notes									0.625%
Calculation of weighted average common shares
Weighted average common shares, basic	12,805,000		12,416,000		12,762,000	12,254,000
Effect of dilutive securities
Effect of stock options (in shares)	810,000		1,176,000		777,000	1,363,000
Effect of dilutive share awards (in shares)	194,000		135,000		191,000	177,000
Effect of Convertible Senior Notes (in shares)	1,099,000		420,000		892,000	733,000
Weighted average common shares, diluted	14,908,000		14,147,000		14,622,000	14,527,000
Common stock repurchases
Value of common stock authorized to be repurchased							$ 150,000	$ 100,000
Purchase of treasury stock (in shares)					17,501	156,731
Treasury Stock, Value, Acquired, Cost Method		$ 3,976	$ 35,003	$ 11,000	$ 4,000	$ 46,000
Remaining authorized repurchase amount	$ 181,200				$ 181,200
Employee stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	100,000		400,000