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Fair Value Measurements (Table) | 9 Months Ended
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Jun. 30, 2017
Fair Value Disclosures [Abstract] |
Fair value measurements table | The following tables summarize, by level within the fair value hierarchy, our assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2017 and September 30, 2016. Assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement.
| Quoted Prices in Active Markets (Level 1) |  | Significant Other Observable Inputs (Level 2)(1) |  | Significant Other Unobservable Inputs (Level 3) |  | Netting and Cash Collateral |  | June 30, 2017
| (In thousands)
Assets: |  |  |  |  |  |  |  |  |
Financial instruments | $ | — |  |  | $ | 3,228 |  |  | $ | — |  |  | $ | — |  |  | $ | 3,228 |
Available-for-sale securities |  |  |  |  |  |  |  |  |
Registered investment companies | 39,406 |  |  | — |  |  | — |  |  | — |  |  | 39,406 |
Bond mutual funds | 15,892 |  |  | — |  |  | — |  |  | — |  |  | 15,892 |
Bonds | — |  |  | 31,429 |  |  | — |  |  | — |  |  | 31,429 |
Money market funds | — |  |  | 2,884 |  |  | — |  |  | — |  |  | 2,884 |
Total available-for-sale securities | 55,298 |  |  | 34,313 |  |  | — |  |  | — |  |  | 89,611 |
Total assets | $ | 55,298 |  |  | $ | 37,541 |  |  | $ | — |  |  | $ | — |  |  | $ | 92,839 |
Liabilities: |  |  |  |  |  |  |  |  |
Financial instruments | $ | — |  |  | $ | 109,372 |  |  | $ | — |  |  | $ | — |  |  | $ | 109,372 |
| Quoted Prices in Active Markets (Level 1) |  | Significant Other Observable Inputs (Level 2)(1) |  | Significant Other Unobservable Inputs (Level 3) |  | Netting and Cash Collateral(2) |  | September 30, 2016
| (In thousands)
Assets: |  |  |  |  |  |  |  |  |
Financial instruments | $ | — |  |  | $ | 44,141 |  |  | $ | — |  |  | $ | (32,515 | ) |  | $ | 11,626 |
Hedged portion of gas stored underground | 52,578 |  |  | — |  |  | — |  |  | — |  |  | 52,578 |
Available-for-sale securities |  |  |  |  |  |  |  |  |
Registered investment companies | 38,677 |  |  | — |  |  | — |  |  | — |  |  | 38,677 |
Bonds | — |  |  | 31,394 |  |  | — |  |  | — |  |  | 31,394 |
Money market funds | — |  |  | 2,630 |  |  | — |  |  | — |  |  | 2,630 |
Total available-for-sale securities | 38,677 |  |  | 34,024 |  |  | — |  |  | — |  |  | 72,701 |
Total assets | $ | 91,255 |  |  | $ | 78,165 |  |  | $ | — |  |  | $ | (32,515 | ) |  | $ | 136,905 |
Liabilities: |  |  |  |  |  |  |  |  |
Financial instruments | $ | — |  |  | $ | 323,684 |  |  | $ | — |  |  | $ | (82,865 | ) |  | $ | 240,819 |
(1) | Our Level 2 measurements consist of over-the-counter options and swaps which are valued using a market-based approach in which observable market prices are adjusted for criteria specific to each instrument, such as the strike price, notional amount or basis differences, municipal and corporate bonds which are valued based on the most recent available quoted market prices and money market funds which are valued at cost.
(2) | This column reflects adjustments to our gross financial instrument assets and liabilities to reflect netting permitted under our master netting agreements and the relevant authoritative accounting literature. As of September 30, 2016, we had $50.4 million of cash held in margin accounts to collateralize certain financial instruments. Of this amount, $43.6 million was used to offset current and noncurrent risk management liabilities under master netting arrangements with the remaining $6.8 million classified as current risk management assets.
Schedule of Available-for-sale Securities Reconciliation Table | Available-for-sale securities are comprised of the following:
| Amortized Cost |  | Gross Unrealized Gain |  | Gross Unrealized Loss |  | Fair Value
| (In thousands)
As of June 30, 2017 |  |  |  |  |  |  |
Domestic equity mutual funds | $ | 25,236 |  |  | $ | 7,749 |  |  | $ | (17 | ) |  | $ | 32,968 |
Foreign equity mutual funds | 4,581 |  |  | 1,857 |  |  | — |  |  | 6,438 |
Bond mutual funds | 15,928 |  |  | — |  |  | (36 | ) |  | 15,892 |
Bonds | 31,407 |  |  | 52 |  |  | (30 | ) |  | 31,429 |
Money market funds | 2,884 |  |  | — |  |  | — |  |  | 2,884 |
| $ | 80,036 |  |  | $ | 9,658 |  |  | $ | (83 | ) |  | $ | 89,611 |
As of September 30, 2016 |  |  |  |  |  |  |
Domestic equity mutual funds | $ | 26,692 |  |  | $ | 6,419 |  |  | $ | (590 | ) |  | $ | 32,521 |
Foreign equity mutual funds | 4,954 |  |  | 1,202 |  |  | — |  |  | 6,156 |
Bonds | 31,296 |  |  | 108 |  |  | (10 | ) |  | 31,394 |
Money market funds | 2,630 |  |  | — |  |  | — |  |  | 2,630 |
| $ | 65,572 |  |  | $ | 7,729 |  |  | $ | (600 | ) |  | $ | 72,701 |
Other fair value measurements table | The following table presents the carrying value and fair value of our debt as of June 30, 2017 and September 30, 2016:
| June 30, 2017 |  | September 30, 2016
| (In thousands)
Carrying Amount | $ | 3,085,000 |  |  | $ | 2,460,000 |
Fair Value | $ | 3,388,003 |  |  | $ | 2,844,990 |

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- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details
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- Definition Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19190-110258 + Details
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