Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Basic Earnings Per Share
Net Income	$ 665,563	$ 601,443	$ 511,406
Less: Income allocated to participating securities	465	444	416
Net Income available to common shareholders	$ 665,098	$ 600,999	$ 510,990
Basic weighted average shares outstanding	129,779	122,788	117,200
Net Income per share — Basic	$ 5.12	$ 4.89	$ 4.36
Earnings Per Share, Diluted [Abstract]
Net Income available to common shareholders	$ 665,098	$ 600,999	$ 510,990
Effect of dilutive shares	0	0	0
Net Income available to common shareholders	$ 665,098	$ 600,999	$ 510,990
Basic weighted average shares outstanding	129,779	122,788	117,200
Dilutive shares	55	84	261
Diluted weighted average shares outstanding	129,834	122,872	117,461
Net Income per share — Diluted	$ 5.12	$ 4.89	$ 4.35