Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Basic Earnings Per Share
Net income	$ 217,678	$ 178,673
Less: Income allocated to participating securities	151	136
Income available to common shareholders	$ 217,527	$ 178,537
Basic weighted average shares outstanding (in shares)	127,034	121,113
Net income per share - Basic (USD per share)	$ 1.71	$ 1.47
Diluted Earnings Per Share
Income available to common shareholders	$ 217,527	$ 178,537
Effect of dilutive shares	0	0
Income available to common shareholders	$ 217,527	$ 178,537
Basic weighted average shares outstanding (in shares)	127,034	121,113
Dilutive shares (in shares)	0	246
Diluted weighted average shares outstanding (in shares)	127,034	121,359
Net income per share - Diluted (USD per share)	$ 1.71	$ 1.47