FAIR VALUE - Financial Instruments by Fair-value Hierarchy Level (Details) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and government-agency securities	$ 684,224,000		$ 661,116,000
Corporate investments (includes $100,616 and $67,626 measured at fair value as of June 30, 2016 and December 31,2015, respectively)	1,036,238,000	$ 176,678,000	213,988,000
Derivative asset	5,069,000		204,226,000
Derivative liabilities	(17,003,000)		(304,437,000)
Transfers between level II and I	0	$ 0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	789,489,000		734,617,000
Total liabilities	(40,623,000)		(32,723,000)
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and government-agency securities	684,224,000		661,116,000
Fair Value, Measurements, Recurring | Corporate investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate investments (includes $100,616 and $67,626 measured at fair value as of June 30, 2016 and December 31,2015, respectively)	100,616,000		67,626,000
Fair Value, Measurements, Recurring | Foreign-currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	4,649,000		5,875,000
Derivative liabilities	(14,916,000)		(3,286,000)
Fair Value, Measurements, Recurring | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	(24,995,000)		(28,494,000)
Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(712,000)		(943,000)
Fair Value, Measurements, Recurring | Level I
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	684,224,000		661,116,000
Total liabilities	0		0
Fair Value, Measurements, Recurring | Level I | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and government-agency securities	684,224,000		661,116,000
Fair Value, Measurements, Recurring | Level I | Corporate investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate investments (includes $100,616 and $67,626 measured at fair value as of June 30, 2016 and December 31,2015, respectively)	0		0
Fair Value, Measurements, Recurring | Level I | Foreign-currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0		0
Derivative liabilities	0		0
Fair Value, Measurements, Recurring | Level I | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0		0
Fair Value, Measurements, Recurring | Level I | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Fair Value, Measurements, Recurring | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	78,684,000		47,751,000
Total liabilities	(15,628,000)		(4,229,000)
Fair Value, Measurements, Recurring | Level II | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and government-agency securities	0		0
Fair Value, Measurements, Recurring | Level II | Corporate investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate investments (includes $100,616 and $67,626 measured at fair value as of June 30, 2016 and December 31,2015, respectively)	74,035,000		41,876,000
Fair Value, Measurements, Recurring | Level II | Foreign-currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	4,649,000		5,875,000
Derivative liabilities	(14,916,000)		(3,286,000)
Fair Value, Measurements, Recurring | Level II | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0		0
Fair Value, Measurements, Recurring | Level II | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(712,000)		(943,000)
Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	26,581,000		25,750,000
Total liabilities	(24,995,000)		(28,494,000)
Fair Value, Measurements, Recurring | Level III | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and government-agency securities	0		0
Fair Value, Measurements, Recurring | Level III | Corporate investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate investments (includes $100,616 and $67,626 measured at fair value as of June 30, 2016 and December 31,2015, respectively)	26,581,000		25,750,000
Fair Value, Measurements, Recurring | Level III | Foreign-currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0		0
Derivative liabilities	0		0
Fair Value, Measurements, Recurring | Level III | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	(24,995,000)		(28,494,000)
Fair Value, Measurements, Recurring | Level III | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 0		$ 0