Shareholders' Equity - Schedule of Components of Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2024	Mar. 31, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock outstanding, beginning balance (in shares)		148,492,783			148,492,783
Shareholders' equity, beginning balance	$ 11,273,209	$ 10,870,064	$ 9,836,274	$ 9,419,091	$ 10,870,064	$ 9,419,091
Net income	432,023	311,292	357,671	271,860	743,315	629,531
Other comprehensive income (loss)	27,108	(49,936)	(30,333)	22,218	$ (22,828)	(8,115)
Cash dividends	(121,667)	(119,898)	(106,173)	(104,552)
Public and other stock offerings	4,025	257,768	143,814	223,779
Stock-based compensation plans	$ 3,941	3,919	3,952	3,878
Common stock outstanding, ending balance (in shares)	150,874,552				150,874,552
Shareholders' equity, ending balance	$ 11,618,639	$ 11,273,209	$ 10,205,205	$ 9,836,274	$ 11,618,639	$ 10,205,205
Cash dividends per share (USD per share)	$ 0.805	$ 0.805	$ 0.740	$ 0.74	$ 1.61	$ 1.48
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock outstanding, beginning balance (in shares)	150,834,397	148,492,783	143,155,761	140,896,598	148,492,783	140,896,598
Shareholders' equity, beginning balance	$ 754	$ 742	$ 716	$ 704	$ 742	$ 704
Public and other stock offerings (in shares)	34,687	2,177,864	1,316,930	2,147,210
Public and other stock offerings		$ 11	$ 6	$ 11
Stock-based compensation plans (in shares)	5,468	163,750	11,959	111,953
Stock-based compensation plans		$ 1		$ 1
Common stock outstanding, ending balance (in shares)	150,874,552	150,834,397	144,484,650	143,155,761	150,874,552	144,484,650
Shareholders' equity, ending balance	$ 754	$ 754	$ 722	$ 716	$ 754	$ 722
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	6,945,795	6,684,120	6,065,763	5,838,118	6,684,120	5,838,118
Public and other stock offerings	4,025	257,757	143,808	223,768
Stock-based compensation plans	3,941	3,918	3,952	3,877
Shareholders' equity, ending balance	6,953,761	6,945,795	6,213,523	6,065,763	6,953,761	6,213,523
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	468,592	518,528	391,330	369,112	518,528	369,112
Other comprehensive income (loss)	27,108	(49,936)	(30,333)	22,218
Shareholders' equity, ending balance	495,700	468,592	360,997	391,330	495,700	360,997
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	3,858,068	3,666,674	3,378,465	3,211,157	3,666,674	3,211,157
Net income	432,023	311,292	357,671	271,860
Cash dividends	(121,667)	(119,898)	(106,173)	(104,552)
Shareholders' equity, ending balance	$ 4,168,424	$ 3,858,068	$ 3,629,963	$ 3,378,465	$ 4,168,424	$ 3,629,963