Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2023	Mar. 31, 2022
Basic Earnings Per Share
Net income	$ 357,671	$ 271,860	$ 324,999	$ 249,209	$ 629,531	$ 574,208
Less: Income allocated to participating securities	212		202		381	379
Income available to common shareholders	$ 357,459		$ 324,797		$ 629,150	$ 573,829
Basic weighted average shares outstanding (in shares)	143,941		136,834		142,881	135,259
Net income per share - Basic (USD per share)	$ 2.48		$ 2.37		$ 4.40	$ 4.24
Diluted Earnings Per Share
Income available to common shareholders	$ 357,459		$ 324,797		$ 629,150	$ 573,829
Effect of dilutive shares	0		0		0	0
Income available to common shareholders	$ 357,459		$ 324,797		$ 629,150	$ 573,829
Basic weighted average shares outstanding (in shares)	143,941		136,834		142,881	135,259
Dilutive shares (in shares)	46		416		82	211
Diluted weighted average shares outstanding (in shares)	143,987		137,250		142,963	135,470
Net income per share - Diluted (USD per share)	$ 2.48		$ 2.37		$ 4.40	$ 4.24