LONG-TERM DEBT / INTEREST EXPENSE COMPONENTS OF CONVERTIABLE DEBT (Details) - USD ($)	Dec. 31, 2015	Aug. 10, 2015	Dec. 31, 2014
Liability component
Net carrying amount	$ 1,452,454,000		$ 1,342,378,000
Convertible senior notes | 1.5% Convertible Senior Notes Due 2020
Liability component
Principal	287,500,000	$ 287,500,000.0
Conversion feature	(46,271,000)
Discount related to debt issuance costs	(6,144,000)
Net carrying amount	235,085,000		$ 0
Equity component
Conversion feature	49,680,000
Discount related to debt issuance costs	(1,421,000)
Deferred taxes	(17,750,000)
Net amount recorded in additional paid-in capital	$ 30,509,000