v3.26.1
Revenue from Contracts with Customers (Schedule of Disaggregation of Revenue) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers $ 473,974 $ 527,430 $ 2,020,871 $ 1,776,653
Alternative Revenue Programs 5,265 1,885 3,547 10,200
Derivative Financial Instruments 58,258 2,515 22,959 24,409
Total Revenues 537,497 531,830 2,047,377 1,811,262
Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues 302,516 306,402 984,561 873,901
Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues 69,559 67,982 212,558 207,916
Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues 165,422 157,446 850,258 729,445
Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 511,034 565,104 2,133,512 1,890,781
Alternative Revenue Programs 5,265 1,885 3,547 10,200
Derivative Financial Instruments 58,258 2,515 22,959 24,409
Total Revenues 574,557 569,504 2,160,018 1,925,390
Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 244,258 303,887 961,602 849,492
Alternative Revenue Programs 0 0 0 0
Derivative Financial Instruments 58,258 2,515 22,959 24,409
Total Revenues 302,516 306,402 984,561 873,901
Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 106,541 105,579 324,905 321,765
Alternative Revenue Programs 0 0 0 0
Derivative Financial Instruments 0 0 0 0
Total Revenues 106,541 105,579 324,905 321,765
Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 160,235 155,638 847,005 719,524
Alternative Revenue Programs 5,265 1,885 3,547 10,200
Derivative Financial Instruments 0 0 0 0
Total Revenues 165,500 157,523 850,552 729,724
All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Alternative Revenue Programs 0 0 0 0
Derivative Financial Instruments 0 0 0 0
Total Revenues 0 0 0 0
Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (37,060) (37,674) (112,641) (114,128)
Alternative Revenue Programs 0 0 0 0
Derivative Financial Instruments 0 0 0 0
Total Revenues [1] (37,060) (37,674) (112,641) (114,128)
Production of Natural Gas        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 235,036 300,137 937,713 836,000
Production of Natural Gas | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 235,036 300,137 937,713 836,000
Production of Natural Gas | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 235,036 300,137 937,713 836,000
Production of Natural Gas | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Natural Gas | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Natural Gas | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Natural Gas | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Crude Oil        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (146) 434 585 1,341
Production of Crude Oil | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (146) 434 585 1,341
Production of Crude Oil | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (146) 434 585 1,341
Production of Crude Oil | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Crude Oil | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Crude Oil | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Production of Crude Oil | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Processing        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 245 267 609 881
Natural Gas Processing | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 245 267 609 881
Natural Gas Processing | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 245 267 609 881
Natural Gas Processing | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Processing | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Processing | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Processing | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Gathering Service        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 3,723 2,519 9,113 9,200
Natural Gas Gathering Service | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 3,723 2,519 9,113 9,200
Natural Gas Gathering Service | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 3,723 2,519 9,113 9,200
Natural Gas Gathering Service | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Gathering Service | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Gathering Service | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Gathering Service | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Transportation Service        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 75,333 75,029 267,179 256,172
Natural Gas Transportation Service | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 101,428 101,874 346,680 337,736
Natural Gas Transportation Service | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Transportation Service | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 80,867 80,235 244,923 243,921
Natural Gas Transportation Service | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 20,561 21,639 101,757 93,815
Natural Gas Transportation Service | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Transportation Service | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (26,095) (26,845) (79,501) (81,564)
Natural Gas Storage Service        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 14,964 14,424 44,172 43,510
Natural Gas Storage Service | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 25,699 25,028 76,513 75,309
Natural Gas Storage Service | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Storage Service | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 25,699 25,028 76,513 75,309
Natural Gas Storage Service | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Storage Service | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Storage Service | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (10,735) (10,604) (32,341) (31,799)
Natural Gas Residential Sales        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 121,502 118,551 642,481 532,001
Natural Gas Residential Sales | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 121,502 118,551 642,481 532,001
Natural Gas Residential Sales | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Residential Sales | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Residential Sales | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 121,502 118,551 642,481 532,001
Natural Gas Residential Sales | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Residential Sales | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Commercial Sales        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 14,129 15,349 92,893 77,194
Natural Gas Commercial Sales | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 14,129 15,349 92,893 77,194
Natural Gas Commercial Sales | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Commercial Sales | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Commercial Sales | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 14,129 15,349 92,893 77,194
Natural Gas Commercial Sales | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Commercial Sales | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Industrial Sales        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 884 731 4,847 4,003
Natural Gas Industrial Sales | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 885 732 4,852 4,007
Natural Gas Industrial Sales | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Industrial Sales | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Industrial Sales | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 885 732 4,852 4,007
Natural Gas Industrial Sales | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Natural Gas Industrial Sales | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (1) (1) (5) (4)
Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 8,304 (11) 21,279 16,351
Other | Operating Segments        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 8,533 213 22,073 17,112
Other | Operating Segments | Integrated Upstream and Gathering        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 5,400 530 13,582 2,070
Other | Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers (25) 316 3,469 2,535
Other | Operating Segments | Utility        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 3,158 (633) 5,022 12,507
Other | All Other        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers 0 0 0 0
Other | Corporate and Intersegment Eliminations        
Disaggregation of Revenue [Line Items]        
Total Revenues from Contracts with Customers $ (229) $ (224) $ (794) $ (761)
[1] Corporate and All Other categories primarily represent other non-segment business activities and eliminating entries.