FAIR VALUE MEASUREMENTS AND FINANCIAL INSTRUMENTS - Schedule of Carrying Amount and Estimated Fair Values of the Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Actual and estimated fair values of the financial instruments
Derivative liability	$ 4,989,000	$ 3,210,000
FILO Asset-based Term Loan Facility | FILO Term Loan | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	264,768	264,086
FILO Asset-based Term Loan Facility | FILO Term Loan | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	267,204	260,125
Notes | Notes | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	177,440	175,504
Notes | Notes | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	134,854	131,628
Tranche B-1 | Amended Term Loan Facility Due March 2021 | Term Loan Facility | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	0	147,289
Tranche B-1 | Amended Term Loan Facility Due March 2021 | Term Loan Facility | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	0	145,080
Tranche B-2 | Amended Term Loan Facility Due March 2021 | Term Loan Facility | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Long-term debt	446,799	554,760
Tranche B-2 | Amended Term Loan Facility Due March 2021 | Term Loan Facility | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Long-term debt	430,938	511,766
Forward contracts for the issuance of convertible preferred stock | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Derivative asset	0	88,942
Forward contracts for the issuance of convertible preferred stock | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Derivative asset	0	88,942
Interest rate swaps | Level 2 | Carrying Amount
Actual and estimated fair values of the financial instruments
Derivative liability	4,989	3,210
Interest rate swaps | Level 2 | Fair Value
Actual and estimated fair values of the financial instruments
Derivative liability	$ 4,989	$ 3,210