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CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (PARENTHETICALS) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017
Other Comprehensive Income Loss Tax Portion Attributable To Parent Abstract |  |  |  |
Unrealized holding gains (losses) on available-for-sale securities, tax | $ (276) | $ 879 | $ (338) | $ 403
Interest Rate Contract [Member] |  |  |  |
Schedule of Other Comprehensive Income (Loss), Tax, Cash Flow Hedges [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax | 6,575 | 2,432 | 6,026 | 54,861
Commodity Contract [Member] |  |  |  |
Schedule of Other Comprehensive Income (Loss), Tax, Cash Flow Hedges [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax | $ 0 | $ 0 | $ 0 | $ 3,183

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