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FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Dec. 31, 2018
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Debt Instrument [Line Items] |  |
Unamortized debt issuance costs | $ 28,426 | $ 30,733
Senior notes | 6.625% senior unsecured notes due 2023 |  |
Debt Instrument [Line Items] |  |
Unamortized debt issuance costs | 4,000 |
Senior notes | 6.000% senior unsecured notes due 2024 |  |
Debt Instrument [Line Items] |  |
Unamortized debt issuance costs | 8,100 |
Senior notes | 6.375% senior unsecured notes due 2025 |  |
Debt Instrument [Line Items] |  |
Unamortized debt issuance costs | 11,700 |
Senior notes | 6.375% senior unsecured notes due 2026 |  |
Debt Instrument [Line Items] |  |
Unamortized debt issuance costs | 4,700 |
Carry value | Senior notes |  |
Debt Instrument [Line Items] |  |
Carrying value of notes | 2,000,000 |
Fair value | Senior notes |  |
Debt Instrument [Line Items] |  |
Carrying value of notes | $ 1,600,000 |

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