v3.26.1
Capitalization (Schedule of Changes in Common Stock Equity) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Dec. 17, 2025
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Mar. 31, 2025
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Beginning balance (in shares)       90,379,095  
Beginning balance       $ 3,094,604  
Net Income Available for Common Stock   $ 247,668 $ 216,358 429,313 $ 261,344
Dividends Declared on Common Stock   (50,840) (46,555) (101,674) (93,226)
Other Comprehensive Income (Loss), Net of Tax   $ 34,101 $ (146,822) $ 60,333 $ (207,499)
Ending balance (in shares)   95,027,447   95,027,447  
Ending balance   $ 3,824,499   $ 3,824,499  
Dividends per share (in dollars per share)   $ 0.535 $ 0.515 $ 1.07 $ 1.030
Sale of Common Stock          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Common Stock Issued from Sale of Common Stock (in shares) 4,402,513     4,402,513  
Stock and Benefit Plans          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Common Stock Issued Under Stock and Benefit Plans (in shares)       245,839  
Common Stock          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Beginning balance (in shares)   95,017,000 90,613,000 90,379,000 91,006,000
Beginning balance   $ 95,017 $ 90,613 $ 90,379 $ 91,006
Common Stock Issued Under Stock and Benefit Plans (in shares)   10,000 11,000 245,000 167,000
Common Stock Issued Under Stock and Benefit Plans   $ 10 $ 11 $ 245 $ 167
Ending balance (in shares)   95,027,000 90,398,000 95,027,000 90,398,000
Ending balance   $ 95,027 $ 90,398 $ 95,027 $ 90,398
Common Stock | Sale of Common Stock          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Common Stock Issued from Sale of Common Stock (in shares)   0   4,403,000  
Common Stock Issued from Sale of Common Stock   $ 0   $ 4,403  
Common Stock | Share Repurchase Plan          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Share Repurchases (in shares)     (226,000)   (775,000)
Share Repurchases     $ (226)   $ (775)
Paid In Capital          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Beginning balance   1,382,593 1,039,705 1,050,918 1,045,487
Share-Based Payment Expense [1]   5,118 5,135 8,545 9,225
Ending balance   1,388,193 1,042,822 1,388,193 1,042,822
Paid In Capital | Sale of Common Stock          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Common Stock Issued from Sale of Common Stock   (172)   334,000  
Paid In Capital | Stock and Benefit Plans          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Common Stock Issued Under Stock and Benefit Plans   654 604    
Share Repurchases       (5,270) (2,906)
Paid In Capital | Share Repurchase Plan          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Share Repurchases     (2,622)   (8,984)
Earnings Reinvested in the Business          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Beginning balance   2,143,340 1,698,648 2,012,529 1,727,326
Net Income Available for Common Stock   247,668 216,358 429,313 261,344
Dividends Declared on Common Stock   (50,840) (46,555) (101,674) (93,226)
Share Repurchases   0 (13,085) 0 (40,078)
Ending balance   2,340,168 1,855,366 2,340,168 1,855,366
Earnings Reinvested in the Business | Share Repurchase Plan          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Share Repurchases     (13,085)   (40,078)
Accumulated Other Comprehensive Income (Loss)          
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Beginning balance   (32,990) (76,153) (59,222) (15,476)
Other Comprehensive Income (Loss), Net of Tax   34,101 (146,822) 60,333 (207,499)
Ending balance   $ 1,111 $ (222,975) $ 1,111 $ (222,975)
[1] Paid in Capital includes compensation costs associated with performance shares and/or restricted stock awards. The expense is included within Net Income Available For Common Stock, net of tax benefits.