BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic and diluted net (loss) income per share
Net (loss) income, basic	$ (33,895)	$ 40,321	$ (12,565)	$ 116,238
Effect of dilutive securities:
Net (loss) income, diluted	(33,895)	45,176	(12,565)	129,089
Reconciliation of basic and diluted shares
Shares used in calculating basic net (loss) income per common share	67,841,665	64,048,673	66,122,521	63,521,491
Options to purchase shares of common stock and RSUs (in shares)		2,262,445		2,305,428
Shares used in calculating diluted net (loss) income per common share	67,841,665	82,856,912	66,122,521	81,251,074
Net (loss) income per share, basic (in dollars per share)	$ (0.50)	$ 0.63	$ (0.19)	$ 1.83
Net (loss) income per share, diluted (in dollars per share)	$ (0.50)	$ 0.55	$ (0.19)	$ 1.59
2.25% Convertible subordinated notes due June 2013 (2013 Notes)
Computation of basic and diluted net income (loss) per common share
Notes stated interest rate percentage	2.25%		2.25%
Effect of dilutive securities:
Interest on convertible notes, net of tax		128
Debt issuance costs, net of tax		17
Debt discount amortization, net of tax		316
Reconciliation of basic and diluted shares
Notes convertible into common stock (in shares)		1,121,639
2.50% convertible senior notes due November 2017 (2017 Notes)
Computation of basic and diluted net income (loss) per common share
Notes stated interest rate percentage	2.50%		2.50%
Effect of dilutive securities:
Interest on convertible notes, net of tax		1,853		5,469
Debt issuance costs, net of tax		245		723
Debt discount amortization, net of tax		$ 2,296		$ 6,659
Reconciliation of basic and diluted shares
Notes convertible into common stock (in shares)		15,424,155		15,424,155
1.125% convertible senior notes due 2018 (2018 Notes)
Computation of basic and diluted net income (loss) per common share
Notes stated interest rate percentage	1.125%		1.125%
1.875% convertible senior notes due 2020 (2020 Notes)
Computation of basic and diluted net income (loss) per common share
Notes stated interest rate percentage	1.875%		1.875%