DEBT - COVERTIBLE SUBORDINATED NOTES (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares
Debt Instrument [Line Items]
Debt, Current	$ 424,900,000	$ 347,100,000
Payments On Zero Coupon Subordinated Notes	$ 1,300,000	$ 18,900,000	$ 21,500,000
Common stock issued upon conversion of zero-coupon subordinated notes (in shares) | shares	0	100,000	100,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt to EBITDA (leverage) ratio		3,600,000
Zero-coupon convertible subordinated notes [Member]
Debt Instrument [Line Items]
Principal amount at maturity of zero-coupon subordinated notes outstanding	$ 105,400,000	$ 106,900,000
Issued price per principal amount at maturity	$ 671.65
Principal amount of zero-coupon subordinated notes		$ 1,000.0
Annual yield to maturity		2.00%
Stock conversion rate for zero-coupon subordinated notes (per thousand) | shares		13.4108
Minimum number of trading days in a period the common stock sale price must meet a specified threshold to trigger conversion price (in days)		20
Number of consecutive trading days ending on the last trading day of the preceding quarter for the common stock sale price to reach a specified threshold to trigger conversion price (in days)		30
Common stock sales price threshold, beginning		120.00%
Common stock sales price threshold, declining per quarter		0.1282%
Common stock sales price threshold, ending		110.00%
Zero Coupon Convertible Subordinated Notes Conversion Trigger Price | $ / shares	$ 75.11
Principal Amount At Maturity Of Zero Coupon Subordinated Notes Converted	$ 1,500,000	$ 21,900,000
Value Of Cash And Common Stock In Connection With Conversions Of Zero Coupon Subordinated Notes Settled In Current Period	1,300,000	28,700,000
Payments On Zero Coupon Subordinated Notes	$ 1,300,000	$ 18,900,000
Common stock issued upon conversion of zero-coupon subordinated notes (in shares) | shares	0	100,000
Tax Benefit Realized Upon Conversion Of Zero Coupon Convertible Debt	$ 400,000	$ 3,800,000
Contingent cash interest accrual rate period	September 12, 2015 to March 11, 2016
Contingent cash interest accrual rate description		no less than 0.125% of the average market price of a zero-coupon subordinated note for the five trading days ended September 9, 2015, in addition to the continued accrual of the original issue discount
Contingent cash interest accrual rate		0.125%
Number of days used to establish average market price of zero coupon subordinated notes		5
Debt Conversion Date Of Subordinated Notes And Indenture	Oct. 24, 2006