Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Basic Earnings Per Share
Net income	$ 774,398	$ 665,563	$ 601,443
Less: Income allocated to participating securities	508	465	444
Net income available to common shareholders	$ 773,890	$ 665,098	$ 600,999
Basic weighted average shares outstanding (in shares)	137,830	129,779	122,788
Net income per share — Basic (USD per share)	$ 5.61	$ 5.12	$ 4.89
Diluted Earnings Per Share
Net income available to common shareholders	$ 773,890	$ 665,098	$ 600,999
Effect of dilutive shares	0	0	0
Net income available to common shareholders	$ 773,890	$ 665,098	$ 600,999
Basic weighted average shares outstanding (in shares)	137,830	129,779	122,788
Dilutive shares (in shares)	266	55	84
Diluted weighted average shares outstanding (in shares)	138,096	129,834	122,872
Net income per share — Diluted (USD per share)	$ 5.60	$ 5.12	$ 4.89