NET INCOME PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule of Earnings Per Share Basic and Diluted [Line Items]
Net income	$ 17,666	$ 11,875	$ 72,129	$ 38,158
Weighted-average common shares outstanding - basic	65,820	75,531	66,450	75,590
Dilutive effect of employee stock-based awards	1,382	1,882	1,510	1,900
Number of shares used to compute net income per common share - diluted	67,202	77,413	67,960	77,490
Basic net income per common share (in dollars per share)	$ 0.27	$ 0.16	$ 1.09	$ 0.50
Diluted net income per common share (in dollars per share)	$ 0.26	$ 0.15	$ 1.06	$ 0.49
Antidilutive Securities [Abstract]
Antidilutive shares excluded from the diluted net income per common share computation (in shares)			3	32
Stock Compensation Plan [Member]
Antidilutive Securities [Abstract]
Antidilutive shares excluded from the diluted net income per common share computation (in shares)		55