Derivative Instruments - Statement Of Financial Position (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Derivative [Line Items]
Derivative asset, net, gross fair value	$ (40,149)	$ (50,970)
Derivative assets, net, net fair value	(40,149)	(50,970)	$ 2,839	$ 21,921
Current derivative assets
Derivative [Line Items]
Derivative asset, gross fair value	281	186
Derivative asset, amounts netted	(198)	(186)
Derivative assets, net fair value	83	0
Non-current derivative assets
Derivative [Line Items]
Derivative asset, gross fair value	267	228
Derivative asset, amounts netted	0	(122)
Derivative assets, net fair value	267	106
Current derivative liabilities
Derivative [Line Items]
Derivative liability, gross fair value	(31,182)	(42,330)
Derivative liability, amounts netted	198	186
Derivative liability, net fair value	(30,984)	(42,144)
Non-current derivative liabilities
Derivative [Line Items]
Derivative liability, gross fair value	(9,515)	(9,054)
Derivative liability, amounts netted	0	122
Derivative liability, net fair value	$ (9,515)	$ (8,932)