FAIR VALUE MEASUREMENTS AND FINANCIAL INSTRUMENTS - Schedule of Carrying Amount and Estimated Fair Values of the Financial Instruments (Details) - Level 2 - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Senior Credit Facility | Term Loan Facility | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	$ 1,130,148	$ 1,170,486
Senior Credit Facility | Term Loan Facility | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	1,084,942	1,100,257
1.5% Convertible Senior Notes, Due 2020 | Notes | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	253,330	245,273
1.5% Convertible Senior Notes, Due 2020 | Notes | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	$ 187,464	$ 185,794