v3.26.1
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Utility Plant [Abstract]    
Electric plant $ 14,032,220 $ 13,745,675
Natural gas plant 5,563,695 5,428,156
Common plant 1,303,952 1,247,883
Less: Accumulated depreciation and amortization (5,567,949) (5,555,794)
Net utility plant 15,331,918 14,865,920
Other property and investments:    
Goodwill 1,656,513 1,656,513
Other property and investments 288,305 289,861
Total other property and investments 1,944,818 1,946,374
Current assets:    
Cash and cash equivalents 552,814 40,484
Restricted cash 153,416 118,369
Accounts receivable, net of allowance for doubtful accounts of $26,675 and $26,452, respectively 448,856 511,163
Unbilled revenue 272,529 332,087
Materials and supplies, at average cost 280,368 232,947
Fuel and natural gas inventory, at average cost 79,144 83,535
Unrealized gain on derivative instruments 38,293 37,448
GHG emission allowances 1,008 22,788
Prepaid expense and other 122,311 132,669
Power contract acquisition adjustment gain 3,277 3,565
Total current assets 1,952,016 1,515,055
Other long-term and regulatory assets:    
Power cost adjustment mechanism 97,056 143,687
Regulatory assets related to power contracts 3,224 3,705
Other regulatory assets 1,482,098 1,564,693
Unrealized gain on derivative instruments 5,188 11,261
Power contract acquisition adjustment gain 21,384 22,878
Operating lease right-of-use asset 433,194 460,990
Other 372,372 372,230
Total other long-term and regulatory assets 2,414,516 2,579,444
Total assets 21,643,268 20,906,793
Common shareholder’s equity:    
Common stock $0.01 par value, 1,000 shares authorized, 200 shares outstanding 0 0
Additional paid-in capital 3,816,332 3,816,332
Retained earnings 2,066,754 1,815,186
Accumulated other comprehensive income (loss), net of tax 74,724 75,829
Total common shareholder’s equity 5,957,810 5,707,347
Long-term debt:    
First mortgage bonds and senior notes 6,345,000 6,345,000
Pollution control bonds 161,860 161,860
Long-term debt 3,100,000 2,200,000
Debt discount issuance costs and other (187,627) (181,828)
Total long-term debt 9,419,233 8,525,032
Total capitalization 15,377,043 14,232,379
Current liabilities:    
Accounts payable 519,077 642,044
Short-term debt 220,000 487,500
Accrued expenses:    
Taxes 121,433 125,719
Salaries and wages 64,965 84,248
Interest 97,627 80,969
Unrealized loss on derivative instruments 305,722 359,890
Power contract acquisition adjustment loss 959 963
Operating lease liabilities 106,631 104,240
Compliance Obligation, Current 0 22,788
Other 80,261 84,341
Total current liabilities 1,516,675 1,992,702
Other long-term and regulatory liabilities:    
Deferred income taxes 1,073,836 941,823
Unamortized investment tax credits 181,067 186,250
Unrealized loss on derivative instruments 223,375 213,531
Purchased gas adjustment liability 46,842 65,931
Regulatory liabilities 1,119,910 1,087,668
Regulatory liability for deferred income taxes 677,073 698,727
Regulatory liabilities related to power contracts 24,661 26,443
Power contract acquisition adjustment loss 2,265 2,742
Operating lease liabilities 334,762 365,359
Finance lease liabilities 164,681 167,426
Compliance obligation 73,822 96,490
Other deferred credits 827,256 829,322
Total long-term and regulatory liabilities 4,749,550 4,681,712
Commitments and contingencies (Note 8)
Total capitalization and liabilities 21,643,268 20,906,793
Subsidiaries    
Utility Plant [Abstract]    
Electric plant 15,381,353 15,432,322
Natural gas plant 6,108,072 5,973,824
Common plant 1,323,776 1,267,813
Less: Accumulated depreciation and amortization (7,481,283) (7,808,039)
Net utility plant 15,331,918 14,865,920
Other property and investments:    
Other property and investments 61,175 59,550
Total other property and investments 61,175 59,550
Current assets:    
Cash and cash equivalents 21,120 38,767
Restricted cash 153,416 118,369
Accounts receivable, net of allowance for doubtful accounts of $26,675 and $26,452, respectively 448,886 511,297
Unbilled revenue 272,529 332,087
Materials and supplies, at average cost 280,368 232,947
Fuel and natural gas inventory, at average cost 77,700 81,488
Unrealized gain on derivative instruments 38,293 37,448
GHG emission allowances 1,008 22,788
Prepaid expense and other 122,131 132,644
Total current assets 1,415,451 1,507,835
Other long-term and regulatory assets:    
Power cost adjustment mechanism 97,056 143,687
Other regulatory assets 1,482,098 1,564,693
Unrealized gain on derivative instruments 5,188 11,261
Operating lease right-of-use asset 433,194 460,990
Other 369,522 371,515
Total other long-term and regulatory assets 2,387,058 2,552,146
Total assets 19,195,602 18,985,451
Common shareholder’s equity:    
Common stock $0.01 par value, 1,000 shares authorized, 200 shares outstanding 859 859
Additional paid-in capital 4,191,905 4,191,905
Retained earnings 2,218,601 2,006,286
Accumulated other comprehensive income (loss), net of tax 6,553 6,501
Total common shareholder’s equity 6,417,918 6,205,551
Long-term debt:    
First mortgage bonds and senior notes 6,345,000 6,345,000
Pollution control bonds 161,860 161,860
Debt discount issuance costs and other (47,791) (49,176)
Total long-term debt 6,459,069 6,457,684
Total capitalization 12,876,987 12,663,235
Current liabilities:    
Accounts payable 520,108 642,047
Short-term debt 220,000 60,000
Accrued expenses:    
Taxes 122,140 126,240
Salaries and wages 64,965 84,248
Interest 63,445 63,302
Unrealized loss on derivative instruments 305,722 359,890
Operating lease liabilities 106,631 104,240
Compliance Obligation, Current 0 22,788
Other 80,261 84,341
Total current liabilities 1,483,272 1,547,096
Other long-term and regulatory liabilities:    
Deferred income taxes 1,191,653 1,069,426
Unamortized investment tax credits 181,067 186,250
Unrealized loss on derivative instruments 223,375 213,531
Purchased gas adjustment liability 46,842 65,931
Regulatory liabilities 1,118,720 1,086,478
Regulatory liability for deferred income taxes 677,565 699,225
Operating lease liabilities 334,762 365,359
Finance lease liabilities 164,681 167,426
Compliance obligation 73,822 96,490
Other deferred credits 822,856 825,004
Total long-term and regulatory liabilities 4,835,343 4,775,120
Commitments and contingencies (Note 8)  
Total capitalization and liabilities $ 19,195,602 $ 18,985,451