FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2013

FAIR VALUE MEASUREMENTS

Schedule of estimated fair values

	Estimated Fair Value Measurements at Reporting Date Using
Types of Instruments	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets at September 30, 2013:
U.S. government securities	$	42,229	$	—	$	—	$	42,229
U.S. government agency securities	114,180		47,677		—		161,857
U.S. corporate notes	85,302		18,507		—		103,809
U.S. commercial paper	—		133,818		—		133,818
Money market funds	146,459		—		—		146,459
Total assets measured at estimated fair value	$	388,170	$	200,002	$	—	$	588,172
Liabilities at September 30, 2013:
Convertible subordinated notes due 2023	$	—	$	476,531	$	—	$	476,531

	Estimated Fair Value Measurements at Reporting Date Using
Types of Instruments	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets at December 31, 2012:
U.S. government securities	$	27,205	$	—	$	—	$	27,205
U.S. government agency securities	56,969		58,497		—		115,466
U.S. corporate notes	40,472		51,094		—		91,566
U.S. commercial paper	—		23,082		—		23,082
Money market funds	78,646		—		—		78,646
Total assets measured at estimated fair value	$	203,292	$	132,673	$	—	$	335,965
Liabilities at December 31, 2012:
Convertible subordinated notes due 2015	$	—	$	194,050	$	—	$	194,050