Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Basic Earnings Per Share
Net income	$ 178,673	$ 157,646
Less: Income allocated to participating securities	136	135
Income available to common shareholders	$ 178,537	$ 157,511
Basic weighted average shares outstanding (in shares)	121,113	113,800
Net income per share - Basic (USD per share)	$ 1.47	$ 1.38
Income available to common shareholders	$ 178,537	$ 157,511
Effect of dilutive shares	0	0
Income available to common shareholders	$ 178,537	$ 157,511
Dilutive shares (in shares)	246	32
Diluted weighted average shares outstanding (in shares)	121,359	113,832
Net income per share - Diluted (USD per share)	$ 1.47	$ 1.38