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DEBT - Summary of Cash Flow Hedges (Details) - Designated as Hedging Instrument - Interest rate swaps - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
Derivatives, Fair Value [Line Items] |  |
Cash flow hedge derivatives, gross liability | $ 7,604 | $ 13,237
Other non-current assets |  |
Derivatives, Fair Value [Line Items] |  |
Cash flow hedge derivatives, gross asset | 228 | 0
Other accrued liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Cash flow hedge derivatives, gross liability | 4,612 | 4,774
Other long-term liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Cash flow hedge derivatives, gross liability | 2,992 | 8,463
Accumulated other comprehensive loss, net of tax |  |
Derivatives, Fair Value [Line Items] |  |
Accumulated other comprehensive loss, interest rate swaps | (7,568) | (13,434)
Accumulated other comprehensive loss, interest rate swaps, tax provision | 538 | 1,917
Accumulated other comprehensive loss, net of tax | $ (7,030) | $ (11,517)

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