Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	$ 513,836	$ 500,050
Alternative Revenue Programs	5,917	5,556
Derivative Financial Instruments	29,729	19,755
Total Revenues	549,482	525,361
All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Alternative Revenue Programs	0	0
Derivative Financial Instruments	0	0
Total Revenues	0	0
Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(95,630)	(87,666)
Alternative Revenue Programs	0	0
Derivative Financial Instruments	0	0
Total Revenues	(95,630)	(87,666)
Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	219,131	234,264
Alternative Revenue Programs	0	0
Derivative Financial Instruments	29,729	19,755
Total Revenues	248,860	254,019
Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	106,612	94,413
Alternative Revenue Programs	0	0
Derivative Financial Instruments	0	0
Total Revenues	106,612	94,413
Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	61,131	62,588
Alternative Revenue Programs	0	0
Derivative Financial Instruments	0	0
Total Revenues	61,131	62,588
Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	222,592	196,451
Alternative Revenue Programs	5,917	5,556
Derivative Financial Instruments	0	0
Total Revenues	228,509	202,007
Production of Natural Gas
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	217,458	232,661
Production of Natural Gas | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Natural Gas | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Natural Gas | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	217,458	232,661
Production of Natural Gas | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Natural Gas | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Natural Gas | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Crude Oil
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	515	687
Production of Crude Oil | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Crude Oil | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Crude Oil | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	515	687
Production of Crude Oil | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Crude Oil | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Production of Crude Oil | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Processing
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	275	267
Natural Gas Processing | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Processing | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Processing | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	275	267
Natural Gas Processing | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Processing | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Processing | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Gathering Service
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	3,448	4,596
Natural Gas Gathering Service | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Gathering Service | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(57,683)	(57,992)
Natural Gas Gathering Service | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Gathering Service | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Gathering Service | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	61,131	62,588
Natural Gas Gathering Service | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Transportation Service
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	80,944	80,541
Natural Gas Transportation Service | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Transportation Service | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(27,181)	(20,362)
Natural Gas Transportation Service | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Transportation Service | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	81,204	71,618
Natural Gas Transportation Service | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Transportation Service | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	26,921	29,285
Natural Gas Storage Service
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	14,489	12,233
Natural Gas Storage Service | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Storage Service | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(10,504)	(9,059)
Natural Gas Storage Service | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Storage Service | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	24,993	21,292
Natural Gas Storage Service | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Storage Service | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	156,350	146,546
Natural Gas Residential Sales | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Residential Sales | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	156,350	146,546
Natural Gas Commercial Sales
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	22,243	20,281
Natural Gas Commercial Sales | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Commercial Sales | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Commercial Sales | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Commercial Sales | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Commercial Sales | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Commercial Sales | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	22,243	20,281
Natural Gas Industrial Sales
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	1,337	904
Natural Gas Industrial Sales | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Industrial Sales | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(1)	(2)
Natural Gas Industrial Sales | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Industrial Sales | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Industrial Sales | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Natural Gas Industrial Sales | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	1,338	906
Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	16,777	1,334
Other | All Other
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Other | Corporate and Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	(261)	(251)
Other | Exploration and Production | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	883	649
Other | Pipeline and Storage | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	415	1,503
Other | Gathering | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	0	0
Other | Utility | Total Reportable Segments
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	$ 15,740	$ (567)