Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Basic Earnings Per Share
Net income	$ 249,209	$ 217,678
Less: Income allocated to participating securities	166	151
Income available to common shareholders	$ 249,043	$ 217,527
Basic weighted average shares outstanding (in shares)	133,682	127,034
Net income per share - basic (USD per share)	$ 1.86	$ 1.71
Diluted Earnings Per Share
Income available to common shareholders	$ 249,043	$ 217,527
Effect of dilutive shares	0	0
Income available to common shareholders	$ 249,043	$ 217,527
Basic weighted average shares outstanding (in shares)	133,682	127,034
Dilutive shares (in shares)	7	0
Diluted weighted average shares outstanding (in shares)	133,689	127,034
Net income per share - diluted (USD per share)	$ 1.86	$ 1.71