Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020 |
Disaggregation of Revenue [Line Items] | | | | |
Revenue | $ 394,397 | $ 323,019 | $ 1,386,671 | $ 1,258,301 |
Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 222,816 | 94,502 | 638,467 | 385,065 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | (13,281) | 36,726 | (17,351) | 67,663 |
Revenue | 209,535 | 131,228 | 621,116 | 452,728 |
Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 84,063 | 77,813 | 258,532 | 229,278 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Revenue | 84,063 | 77,813 | 258,532 | 229,278 |
Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 48,656 | 33,299 | 145,927 | 103,355 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Revenue | 48,656 | 33,299 | 145,927 | 103,355 |
Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 123,948 | 126,545 | 576,358 | 570,580 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 3,060 | 492 | 10,531 | 7,775 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Revenue | 127,008 | 127,037 | 586,889 | 578,355 |
All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 1 | 20,164 | 1,196 | 92,647 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | (3,537) | 0 | (8,604) |
Revenue | 1 | 16,627 | 1,196 | 84,043 |
Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (74,866) | (62,985) | (226,989) | (189,458) |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 | 0 | 0 |
Revenue | (74,866) | (62,985) | (226,989) | (189,458) |
Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 404,618 | 289,338 | 1,393,491 | 1,191,467 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 3,060 | 492 | 10,531 | 7,775 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | (13,281) | 33,189 | (17,351) | 59,059 |
Revenue | 394,397 | 323,019 | 1,386,671 | 1,258,301 |
Production of Natural Gas [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 184,029 | 76,831 | 539,241 | 297,481 |
Production of Natural Gas [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Natural Gas [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Natural Gas [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Natural Gas [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Natural Gas [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Natural Gas [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 184,029 | 76,831 | 539,241 | 297,481 |
Production of Crude Oil [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 37,695 | 17,018 | 95,783 | 84,949 |
Production of Crude Oil [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Crude Oil [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Crude Oil [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Crude Oil [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Crude Oil [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Production of Crude Oil [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 37,695 | 17,018 | 95,783 | 84,949 |
Natural Gas Processing [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 732 | 435 | 2,056 | 1,838 |
Natural Gas Processing [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Processing [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Processing [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Processing [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Processing [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Processing [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 732 | 435 | 2,056 | 1,838 |
Natural Gas Gathering Service [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Gathering Service [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Gathering Service [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 48,656 | 33,299 | 145,927 | 103,355 |
Natural Gas Gathering Service [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Gathering Service [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Gathering Service [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (48,068) | (33,299) | (144,317) | (103,355) |
Natural Gas Gathering Service [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 588 | 0 | 1,610 | 0 |
Natural Gas Transportation Service [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Transportation Service [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 63,107 | 57,563 | 192,580 | 169,469 |
Natural Gas Transportation Service [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Transportation Service [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 20,201 | 22,473 | 88,736 | 95,112 |
Natural Gas Transportation Service [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Transportation Service [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (17,786) | (20,445) | (55,562) | (59,408) |
Natural Gas Transportation Service [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 65,522 | 59,591 | 225,754 | 205,173 |
Natural Gas Storage Service [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Storage Service [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 20,646 | 20,016 | 62,394 | 58,966 |
Natural Gas Storage Service [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Storage Service [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Storage Service [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Storage Service [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (8,926) | (8,802) | (26,797) | (25,881) |
Natural Gas Storage Service [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 11,720 | 11,214 | 35,597 | 33,085 |
Natural Gas Residential Sales [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Residential Sales [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Residential Sales [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Residential Sales [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 93,079 | 93,853 | 434,728 | 423,547 |
Natural Gas Residential Sales [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Residential Sales [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Residential Sales [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 93,079 | 93,853 | 434,728 | 423,547 |
Natural Gas Commercial Sales [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Commercial Sales [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Commercial Sales [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Commercial Sales [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 10,617 | 10,264 | 56,684 | 56,401 |
Natural Gas Commercial Sales [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Commercial Sales [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Commercial Sales [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 10,617 | 10,264 | 56,684 | 56,401 |
Natural Gas Industrial Sales [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Industrial Sales [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Industrial Sales [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Industrial Sales [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 488 | 616 | 2,778 | 3,029 |
Natural Gas Industrial Sales [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Industrial Sales [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Industrial Sales [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 488 | 616 | 2,778 | 3,029 |
Natural Gas Marketing [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Marketing [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Marketing [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Marketing [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Natural Gas Marketing [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 1 | 19,149 | 651 | 89,662 |
Natural Gas Marketing [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (2) | (341) | (22) | (598) |
Natural Gas Marketing [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (1) | 18,808 | 629 | 89,064 |
Other [Member] | Exploration And Production [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 360 | 218 | 1,387 | 797 |
Other [Member] | Pipeline And Storage [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 310 | 234 | 3,558 | 843 |
Other [Member] | Gathering [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 0 | 0 | 0 |
Other [Member] | Utility [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (437) | (661) | (6,568) | (7,509) |
Other [Member] | All Other [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | 0 | 1,015 | 545 | 2,985 |
Other [Member] | Corporate And Intersegment Eliminations [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | (84) | (98) | (291) | (216) |
Other [Member] | Total Consolidated [Member] | | | | |
Disaggregation of Revenue [Line Items] | | | | |
Revenue from Contracts with Customers | $ 149 | $ 708 | $ (1,369) | $ (3,100) |