Variable Interest Entity - Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Operating revenues	$ 1,158,467	$ 1,484,009
Amortization expense	(164,608)	(146,020)
Interest expense, net	(51,875)	(36,760)
Income before income taxes	365,116	$ 305,617
Variable Interest Entity, Primary Beneficiary | AEK
Variable Interest Entity [Line Items]
Operating revenues	3,333
Amortization expense	(2,166)
Interest expense, net	(1,167)
Income before income taxes	$ 0