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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - INVESTMENTS IN EQUTIY SECURITIES (Details) shares in Thousands, $ in Thousands |  |  | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | --- | ---
Mar. 06, 2019 USD ($) | Jan. 28, 2019 shares | Mar. 31, 2019 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2018 USD ($) | Sep. 30, 2018 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Investments in equity securities |  |  |  |  |  | $ 32,900
Debt conversion ratio |  | 0.2492 |  |  |  |
Proceeds from sale of investments in equity securities, net | $ 34,500 |  |  | $ 34,484 | $ 6,616 |
Pre-tax again investments in equity securities |  |  | $ 1,300 | $ 1,600 |  |
Common Units |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Other ownership interests, units issued (in units) | shares |  | 1,840 |  |  |  |
Dominion Shares |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Other ownership interests, units issued (in units) | shares |  | 458 |  |  |  |

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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References No definition available. + Details
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- Definition Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
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