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DERIVATIVE INSTRUMENTS - INCOME STATEMENT RELATED DISCLOSURES (Details) - Derivatives not designated as hedging instruments: - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | $ (34,175) | $ 8,055 | $ 32,942
Natural Gas Distribution |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | 11,543 | 7,898 | (42,585)
Natural Gas Distribution | Physical commodity contracts |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | 1,232 | (12,303) | (15,756)
Natural Gas Distribution | Financial commodity contracts |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | 1,844 | 5,595 | (7,984)
Natural Gas Distribution | Interest rate contract |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | 8,467 | 14,606 | (18,845)
Energy Services | Physical commodity contracts | Operating revenues |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | (9,311) | 8,912 | 33,034
Energy Services | Physical commodity contracts | Gas purchases |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | (197) | (27,461) | (45,637)
Energy Services | Financial commodity contracts | Gas purchases |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | (24,622) | 26,563 | 45,579
Energy Services | Foreign currency contracts | Gas purchases |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | (379) | 41 | (34)
Home Services and Other | Interest rate contract | Interest expense |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of gain (loss) recognized in income on derivatives | $ 334 | $ 0 | $ 0

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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