Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2025	Jun. 30, 2024
Basic Earnings Per Share
Net income	$ 186,429	$ 485,576	$ 351,858	$ 165,564	$ 432,023	$ 311,292	$ 1,023,863	$ 908,879
Less: Income allocated to participating securities	87			87			422	490
Income available to common shareholders	$ 186,342			$ 165,477			$ 1,023,441	$ 908,389
Basic weighted average shares outstanding (in shares)	159,285			153,309			158,245	151,459
Net income per share - Basic (USD per share)	$ 1.17			$ 1.08			$ 6.47	$ 6.00
Diluted Earnings Per Share
Income available to common shareholders	$ 186,342			$ 165,477			$ 1,023,441	$ 908,389
Effect of dilutive shares	0			0			0	0
Income available to common shareholders	$ 186,342			$ 165,477			$ 1,023,441	$ 908,389
Basic weighted average shares outstanding (in shares)	159,285			153,309			158,245	151,459
Dilutive shares (in shares)	1,886			87			1,553	38
Diluted weighted average shares outstanding (in shares)	161,171			153,396			159,798	151,497
Net income per share - Diluted (USD per share)	$ 1.16			$ 1.08			$ 6.40	$ 6.00