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LONG-TERM DEBT (Details) - Subsequent event $ in Millions | Apr. 29, 2020 USD ($)
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MERC | MERC Senior Notes 2.69% due May 1, 2025 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 50.0
Debt instrument stated interest rate percentage | 2.69%
MGU | MGU Senior Notes 2.69% due May 1, 2025 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 60.0
Debt instrument stated interest rate percentage | 2.69%

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