CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Common stock shares outstanding, balance (in shares) at Sep. 30, 2022		140,896,598
Shareholders' equity, beginning balance at Sep. 30, 2022	$ 9,419,091	$ 704	$ 5,838,118	$ 369,112	$ 3,211,157
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	885,862				885,862
Other comprehensive income (loss)	149,416			149,416
Cash dividends	(430,345)				(430,345)
Common stock issued:
Public offering (in shares)		7,272,261
Public offering	806,949	$ 36	806,913
Direct stock purchase plan (in shares)		64,871
Direct stock purchase plan	7,429		7,429
Retirement savings plan (in shares)		69,716
Retirement savings plan	7,966	$ 1	7,965
1998 Long-term incentive plan (in shares)		189,337
1998 Long-term incentive plan	2,108	$ 1	2,107
Employee stock-based compensation	21,588		21,588
Common stock shares outstanding, ending balance (in shares) at Sep. 30, 2023		148,492,783
Shareholders' equity, ending balance at Sep. 30, 2023	10,870,064	$ 742	6,684,120	518,528	3,666,674
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,042,895				1,042,895
Other comprehensive income (loss)	(52,813)			(52,813)
Cash dividends	(492,950)				(492,950)
Common stock issued:
Public offering (in shares)		6,401,469
Public offering	749,987	$ 32	749,955
Direct stock purchase plan (in shares)		60,756
Direct stock purchase plan	7,129		7,129
Retirement savings plan (in shares)		67,134
Retirement savings plan	7,955	$ 1	7,954
1998 Long-term incentive plan (in shares)		236,703
1998 Long-term incentive plan	2,198	$ 1	2,197
Employee stock-based compensation	$ 23,204		23,204
Common stock shares outstanding, ending balance (in shares) at Sep. 30, 2024	155,258,845	155,258,845
Shareholders' equity, ending balance at Sep. 30, 2024	$ 12,157,669	$ 776	7,474,559	465,715	4,216,619
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,198,754				1,198,754
Other comprehensive income (loss)	9,300			9,300
Cash dividends	(553,761)				(553,761)
Common stock issued:
Public offering (in shares)		5,931,289
Public offering	698,462	$ 30	698,432
Direct stock purchase plan (in shares)		47,422
Direct stock purchase plan	7,231		7,231
Retirement savings plan (in shares)		54,565
Retirement savings plan	8,046		8,046
1998 Long-term incentive plan (in shares)		276,263
1998 Long-term incentive plan	2,685	$ 2	2,683
Employee stock-based compensation	$ 30,504		30,504
Common stock shares outstanding, ending balance (in shares) at Sep. 30, 2025	161,568,384	161,568,384
Shareholders' equity, ending balance at Sep. 30, 2025	$ 13,558,890	$ 808	$ 8,221,455	$ 475,015	$ 4,861,612