SHAREHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 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	12,890,000		12,799,000			12,805,000	12,437,000
Effect of dilutive securities
Effect of stock options (in shares)	726,000		758,000			760,000	1,160,000
Effect of dilutive share awards (in shares)	136,000		110,000			176,000	167,000
Effect of Convertible Senior Notes (in shares)	880,000		183,000			888,000	535,000
Weighted average common shares, diluted	14,632,000		13,850,000			14,629,000	14,299,000
Common stock repurchases
Value of common stock authorized to be repurchased								$ 150,000	$ 100,000
Purchase of treasury stock (in shares)						18,580	205,310
Treasury Stock, Value, Acquired, Cost Method	$ 310	$ 3,976	$ 11,180	$ 35,003	$ 11,000	$ 4,300	$ 57,200
Remaining authorized repurchase amount	$ 180,900					$ 180,900
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		500,000			100,000	400,000
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			100,000