Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024	Sep. 30, 2025
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground	$ 24,725		$ 35,055
Capitalized Costs Exploration and Production Activities Net	2,200,000		2,300,000
Capitalized costs of unproved properties excluded from amortization	$ 133,300		$ 201,000
Full cost ceiling test discount factor (as a percent)	10.00%
Impairment of exploration and production properties	$ 108,300
Increase estimated future net cash flows	$ 495,300
Antidilutive securities (in shares)	4	0
Impairment of Exploration and Production Properties
Summary Of Significant Accounting Policies [Line Items]
Deferred income tax benefit	$ 29,200
Reserve For Gas Replacement
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground	$ 1,300
Reserve For Gas Replacement | Forecast
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground				$ 0
Restricted Stock Units
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period (in shares)	130,252
Granted in fiscal year, weighted average grant date fair value (in USD per share)	$ 58.48
Performance Shares
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period (in shares)	239,042
Granted in fiscal year, weighted average grant date fair value (in USD per share)	$ 55.43
Return on capital, performance cycle (in years)	3 years
Greenhouse gas emissions reductions, performance cycle	3 years
Relative shareholder return, performance cycle	3 years