Details of Selected Financial Statement Captions - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Cash Paid (Received) During The Period For:
Interest	$ 349,222	$ 308,872	$ 249,066
Income taxes:
Federal	(5,000)	8,200	(4,500)
Total income taxes	4,452	15,349	14,968
Non-Cash Transactions:
Capital expenditures included in current liabilities	327,814	299,908	186,912
Interest paid, net of amount capitalized	155,300	163,500	117,900
State of Texas
Income taxes:
State	7,095	5,372	17,200
State of Louisiana
Income taxes:
State	2,357	1,739	2,232
Other states
Income taxes:
State	$ 0	$ 38	$ 36