Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2022	Jun. 30, 2021
Basic Earnings Per Share
Net income	$ 128,547	$ 324,999	$ 249,209	$ 102,411	$ 296,754	$ 217,678	$ 702,755	$ 616,843
Less: Income allocated to participating securities	79			70			465	440
Income available to common shareholders	$ 128,468			$ 102,341			$ 702,290	$ 616,403
Basic weighted average shares outstanding (in shares)	139,881			131,358			136,799	129,185
Net income per share - basic (USD per share)	$ 0.92			$ 0.78			$ 5.13	$ 4.77
Diluted Earnings Per Share
Income available to common shareholders	$ 128,468			$ 102,341			$ 702,290	$ 616,403
Effect of dilutive shares	0			0			0	0
Income available to common shareholders	$ 128,468			$ 102,341			$ 702,290	$ 616,403
Basic weighted average shares outstanding (in shares)	139,881			131,358			136,799	129,185
Dilutive shares (in shares)	346			128			256	44
Diluted weighted average shares outstanding (in shares)	140,227			131,486			137,055	129,229
Net income per share - diluted (USD per share)	$ 0.92			$ 0.78			$ 5.12	$ 4.77