BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2012 2.50% convertible senior notes due November 2017 (2.50% Notes)	Jun. 30, 2012 2.50% convertible senior notes due November 2017 (2.50% Notes)	Jun. 30, 2013 2.50% convertible senior notes due November 2017 (2.50% Notes)	Oct. 31, 2010 2.50% convertible senior notes due November 2017 (2.50% Notes)	Jun. 30, 2013 2.25% Convertible subordinated notes due June 2013 (2.25% Notes)
Computation of basic and diluted net income (loss) per common share
Notes stated interest rate percentage							2.50%	2.50%	2.25%
Basic and diluted net income per share
Net income, basic	$ 15,242	$ 43,123	$ 21,330	$ 75,917
Effect of dilutive securities:
Interest on convertible notes, net of tax					1,808	3,610
Debt issuance costs, net of tax					239	477
Debt discount amortization, net of tax					2,201	4,358
Net income, diluted	$ 15,242	$ 47,371	$ 21,330	$ 84,362
Reconciliation of basic and diluted shares
Shares used in calculating basic net income per common share	65,558,376	63,498,953	65,248,707	63,250,165
Options to purchase shares of common stock and RSUs (in shares)	2,173,600	2,243,221	2,136,434	2,327,156
Notes converted into common stock (in shares)					15,424,155	15,424,155
Shares used in calculating diluted net income per common share	67,731,976	81,166,329	67,385,141	81,001,476
Net income per share, basic (in dollars per share)	$ 0.23	$ 0.68	$ 0.33	$ 1.20
Net income per share, diluted (in dollars per share)	$ 0.23	$ 0.58	$ 0.32	$ 1.04