v3.26.1
Condensed Consolidated Statements Of Capitalization - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Stockholders' equity:    
Common stock, $0.50 par value $ 143,631 $ 143,253
Capital in excess of par value 4,551,801 4,524,517
Retained earnings 2,416,322 2,280,669
Treasury stock, at cost (93,498) (90,983)
Total stockholders' equity 7,018,256 6,857,456
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 3,086,444 3,068,848
Total long-term debt 8,516,167 8,181,848
Current portion of long-term debt 42,312 21,822
Long-term debt, excluding current portion 8,473,855 8,160,026
Less: debt issuance costs and unamortized discount on debt 52,657 49,859
Long-term debt, excluding current portion, net of debt issuance costs and unamortized discount on debt 8,421,198 8,110,167
Total capitalization 15,439,454 14,967,623
Notes Ranging From 0.00% To 0.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 14,213 7,328
Notes Ranging From 1.00% To 1.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 43,292 23,977
Notes Ranging From 2.00% To 2.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 204,207 204,870
Notes Ranging From 3.00% To 3.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 1,249,864 1,252,397
Notes Ranging From 4.00% To 4.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 1,120,240 1,120,564
Notes Ranging From 5.00% To 5.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 412,260 412,260
Notes Ranging From 6.00% To 6.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 26,000 31,000
Notes Ranging From 7.00% To 7.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 4,568 4,652
Notes Ranging From 9.00% To 9.99% [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Long-term debt of subsidiaries 11,800 11,800
Commercial Paper Program [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 384,723 568,000
Notes At 2.40% Due 2031 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 400,000 400,000
Notes At 2.704% Due 2030 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes Ranging From 3.01% To 3.57% Due 2029 Through 2050 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 1,125,000 1,125,000
Notes At 4.276%, Due 2049 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes At 4.80%, Due 2027 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes At 5.125%, Due 2036 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000  
Notes At 5.25%, Due 2035 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes At 5.30%, Due 2052 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes At 5.375%, Due 2034 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable 500,000 500,000
Notes At 5.95%, Due 2033 through 2034 [Member]    
Long-term debt of subsidiaries (substantially collateralized by utility plant):    
Unsecured notes payable $ 20,000 $ 20,000