| Dec 31, 2010 | Dec 31, 2011 | Dec 31, 2012 | Dec 31, 2013 | Dec 31, 2014 | Dec 31, 2015 | Dec 31, 2016 | Dec 31, 2017 | Dec 31, 2018 | Dec 31, 2019 | Dec 31, 2020 | Dec 31, 2021 | Dec 31, 2022 | Dec 31, 2023 | Dec 31, 2024 |
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| Net Income | 142 | 167 | 169 | 182 | 194 | 194 | 198 | 213 | 228 | 233 | 238 | 246 | 260 | 262 | 290 |
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| Depreciation and amortization | 122 | 125 | 129 | 134 | 137 | 143 | 147 | 166 | 169 | 174 | 176 | 179 | 174 | 200 | 228 |
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| Deferred Income Taxes and Tax Credits | 42 | -53 | 26 | 66 | 19 | 39 | 36 | 33 | 11 | 22 | 25 | 24 | -1 | 40 | -18 |
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| Changes in regulatory assets and liabilities | 47 | -68 | -53 | 26 | -32 | -14 | 6 | -57 | -48 | 4 | 36 | 34 | 80 | 5 | -115 |
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| Pension and postretirement benefit plan expense | 15 | 45 | 45 | 46 | 45 | 30 | 30 | 29 | 32 | 28 | 29 | 34 | 29 | 27 | 46 |
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| Contributions to pension and postretirement benefit plans | 66 | 22 | 48 | 33 | 34 | 43 | 45 | 47 | 46 | 49 | 45 | 44 | 44 | 55 | 25 |
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| Income (Loss) from Equity Method Investments | 3 | 1 | -0 | 12 | 12 | 11 | 13 | 11 | 12 | 12 | 12 | 11 | 12 | 12 | 5 |
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| Proceeds from Equity Method Investment, Distribution | -7 | 3 | 19 | 18 | 5 | 12 | 26 | 25 | 31 | 22 | 14 | 12 | 12 | 3 | 8 |
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| Allowance for equity funds used during construction | 17 | 25 | 22 | 15 | 18 | 22 | 22 | 21 | 24 | 27 | 30 | 32 | 37 | 43 | 53 |
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| Other non-cash adjustments to net income, net | - | -4 | -6 | -3 | -5 | -3 | -5 | -8 | -9 | -8 | -10 | -9 | -15 | -8 | -10 |
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| Accounts receivable | -14 | - | - | 30 | -20 | -5 | 3 | -4 | -1 | 6 | 0 | 7 | 82 | 18 | -31 |
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| Accounts payable and other accrued liabilities | 4 | 5 | 11 | -1 | 6 | 2 | 13 | -17 | 30 | -10 | -0 | 18 | -2 | -3 | -9 |
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| Taxes accrued/receivable | -14 | 15 | -1 | 5 | -14 | 1 | 1 | 4 | 5 | 1 | 9 | -18 | -12 | -53 | -84 |
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| Other current assets | 4 | 20 | 4 | 12 | 13 | 15 | 11 | -3 | -13 | 9 | -5 | 8 | -113 | 81 | -17 |
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| Other current liabilities | -14 | 2 | -8 | 2 | 2 | 0 | -3 | 1 | 7 | -1 | 8 | 3 | -5 | -13 | 11 |
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| Other assets | - | - | - | - | - | - | - | - | - | - | - | 11 | -23 | -11 | -32 |
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| Net cash provided by operating activities | 305 | 310 | 249 | 306 | 364 | 353 | 348 | 438 | 492 | 367 | 388 | 363 | 351 | 267 | 594 |
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| Additions to property, plant and equipment | 338 | 338 | 240 | 235 | 274 | 294 | 297 | 285 | 278 | 279 | 311 | 300 | 433 | 611 | 1,009 |
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| Payments received from transmission project joint funding partners | - | - | - | - | - | 11 | 8 | 6 | 22 | 2 | 3 | 6 | 18 | 27 | 84 |
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| Payments to Acquire Partners Interest in Real Estate Partnership, Net of Cash Acquired | 13 | 2 | 0 | - | - | - | - | - | - | - | 14 | 15 | 10 | 3 | 4 |
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| Proceeds from Equity Method Investment, Distribution, Return of Capital | - | - | - | - | - | - | - | - | - | - | - | 14 | 8 | - | - |
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| Payments to Acquire Equity Securities, FV-NI | - | - | - | - | - | - | - | - | - | - | - | 17 | 46 | 12 | 12 |
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| Debt Securities, Held-to-Maturity, Purchase | - | - | - | - | - | - | - | - | - | - | - | - | -31 | -2 | -2 |
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| Proceeds from Sale, Debt Security, Trading, and Equity Security, FV-NI, Held-for-Investment | - | - | - | - | - | - | - | - | - | - | - | 11 | 64 | 9 | 11 |
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| Payments to Acquire Short-term Investments | - | - | - | - | - | - | - | - | - | - | 25 | 25 | 25 | - | - |
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| Proceeds from Maturities, Prepayments and Calls of Short-term Investments | - | - | - | - | - | - | - | - | - | - | - | 50 | 25 | - | - |
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| Other | -5 | -3 | -0 | -3 | -5 | -1 | -1 | -2 | -4 | -2 | -7 | -2 | -5 | -2 | -15 |
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| Net cash used in investing activities | -328 | -332 | -244 | -237 | -272 | -292 | -297 | -283 | -258 | -280 | -347 | -274 | -424 | -590 | -918 |
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| Issuance of long-term debt | 200 | - | 150 | 150 | - | 250 | 120 | - | 220 | 166 | 310 | - | 198 | 872 | 300 |
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| Premium on issuance of long-term debt | - | - | - | - | - | - | - | - | - | - | 31 | - | - | -7 | -0 |
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| Retirement of long-term debt | 1 | 121 | 101 | 71 | 1 | 121 | 101 | 1 | 130 | 166 | 175 | - | 4 | 225 | 50 |
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| Dividends on common stock | 58 | 60 | 69 | 79 | 88 | 97 | 105 | 113 | 121 | 130 | 138 | 146 | 154 | 164 | 177 |
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| Proceeds from Issuance of Common Stock | 49 | 18 | 5 | 0 | 0 | - | - | - | - | - | - | - | - | - | 298 |
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| Acquisition of treasury stock | 1 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 4 | 4 | 5 | 3 | 3 | 3 | 4 |
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| Other | -3 | -1 | -5 | -1 | 2 | -3 | -2 | -0 | -3 | -3 | -4 | -0 | -1 | -0 | -3 |
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| Net cash used in financing activities | 199 | -179 | -7 | -17 | -113 | -3 | -104 | -140 | -43 | -136 | 17 | -149 | 35 | 473 | 365 |
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| Net increase (decrease) in cash and cash equivalents | - | - | - | - | - | - | - | - | - | - | - | -60 | -38 | 150 | 41 |
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| Income taxes | -27 | -12 | 1 | 1 | 11 | 9 | 3 | 15 | 5 | 14 | 10 | 34 | 46 | 6 | 25 |
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| Interest (net of amount capitalized) | 69 | 71 | 71 | 78 | 77 | 79 | 78 | 80 | 81 | 85 | 81 | 83 | 86 | 98 | 109 |
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| Capital Expenditures Incurred but Not yet Paid | 34 | 26 | 27 | 24 | 28 | 24 | 35 | 33 | 30 | 39 | 45 | 54 | 84 | 185 | 168 |
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