Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands | 3 Months Ended |
Dec. 31, 2020 | Dec. 31, 2019 |
Disaggregation of Revenue [Line Items] | | |
Revenue | $ 441,160 | $ 444,188 |
Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 191,705 | 158,398 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | (310) | 7,541 |
Revenue | 191,395 | 165,939 |
Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 87,764 | 72,220 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Revenue | 87,764 | 72,220 |
Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 47,009 | 34,788 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Revenue | 47,009 | 34,788 |
Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 183,407 | 193,965 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 5,594 | 2,860 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Revenue | 189,001 | 196,825 |
All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 1,130 | 35,228 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | (816) |
Revenue | 1,130 | 34,412 |
Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (75,139) | (59,996) |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | 0 | 0 |
Revenue | (75,139) | (59,996) |
Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 435,876 | 434,603 |
Alternative Revenue Programs Outside Scope of Authoritative Guidance on Revenue Recognition | 5,594 | 2,860 |
Derivative Financial Instruments Outside Scope of Authoritative Guidance on Revenue Recognition | (310) | 6,725 |
Revenue | 441,160 | 444,188 |
Production of Natural Gas [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 166,442 | 119,874 |
Production of Natural Gas [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Natural Gas [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Natural Gas [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Natural Gas [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Natural Gas [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Natural Gas [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 166,442 | 119,874 |
Production of Crude Oil [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 24,499 | 37,664 |
Production of Crude Oil [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Crude Oil [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Crude Oil [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Crude Oil [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Crude Oil [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Production of Crude Oil [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 24,499 | 37,664 |
Natural Gas Processing [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 553 | 688 |
Natural Gas Processing [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Processing [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Processing [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Processing [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Processing [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Processing [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 553 | 688 |
Natural Gas Gathering Service [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Gathering Service [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Gathering Service [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 47,009 | 34,788 |
Natural Gas Gathering Service [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Gathering Service [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Gathering Service [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (46,658) | (34,788) |
Natural Gas Gathering Service [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 351 | 0 |
Natural Gas Transportation Service [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Transportation Service [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 64,825 | 53,452 |
Natural Gas Transportation Service [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Transportation Service [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 29,021 | 32,808 |
Natural Gas Transportation Service [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Transportation Service [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (19,590) | (16,986) |
Natural Gas Transportation Service [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 74,256 | 69,274 |
Natural Gas Storage Service [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Storage Service [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 20,517 | 18,426 |
Natural Gas Storage Service [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Storage Service [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Storage Service [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Storage Service [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (8,763) | (7,993) |
Natural Gas Storage Service [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 11,754 | 10,433 |
Natural Gas Residential Sales [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Residential Sales [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Residential Sales [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Residential Sales [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 137,881 | 144,370 |
Natural Gas Residential Sales [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Residential Sales [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Residential Sales [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 137,881 | 144,370 |
Natural Gas Commercial Sales [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Commercial Sales [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Commercial Sales [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Commercial Sales [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 17,195 | 18,841 |
Natural Gas Commercial Sales [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Commercial Sales [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Commercial Sales [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 17,195 | 18,841 |
Natural Gas Industrial Sales [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Industrial Sales [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Industrial Sales [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Industrial Sales [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 922 | 1,270 |
Natural Gas Industrial Sales [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Industrial Sales [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Industrial Sales [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 922 | 1,270 |
Natural Gas Marketing [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Marketing [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Marketing [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Marketing [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Natural Gas Marketing [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 585 | 34,108 |
Natural Gas Marketing [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (20) | (177) |
Natural Gas Marketing [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 565 | 33,931 |
Other [Member] | Exploration And Production [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 211 | 172 |
Other [Member] | Pipeline And Storage [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 2,422 | 342 |
Other [Member] | Gathering [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 0 | 0 |
Other [Member] | Utility [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (1,612) | (3,324) |
Other [Member] | All Other [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | 545 | 1,120 |
Other [Member] | Corporate And Intersegment Eliminations [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | (108) | (52) |
Other [Member] | Total Consolidated [Member] | | |
Disaggregation of Revenue [Line Items] | | |
Revenue from Contracts with Customers | $ 1,458 | $ (1,742) |