v3.25.0.1
Benefit Plans: (Fair Value of Pension Plan Assets) (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Total assets $ 3 $ 3  
U S and International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Investment in securities, percent 57.00% 57.00%  
U S and International Government Bonds      
Defined Benefit Plan Disclosure [Line Items]      
Investment in securities, percent 13.00% 15.00%  
Investment Funds Holding Corporate Bonds      
Defined Benefit Plan Disclosure [Line Items]      
Investment in securities, percent 14.00% 15.00%  
Real Estate and Other Money Markets      
Defined Benefit Plan Disclosure [Line Items]      
Investment in securities, percent 16.00% 13.00%  
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Total assets $ 9,030 $ 8,851 $ 7,939
Pension | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 9,030 8,851  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 8,747 8,579  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 83 117  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | U.S. securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 144 158  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | International securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 525 569  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Investment Funds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 7,317 7,123  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Government bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 238 255  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 409 320  
Pension | Fair Value, Inputs, Level 1, 2 and 3 | Other | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 31 37  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 6,572 6,713  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Cash and cash equivalents | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 83 117  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | U.S. securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 144 158  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | International securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 525 569  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Investment Funds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 5,245 5,366  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Government bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 166 183  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Corporate bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 409 320  
Pension | Quoted Prices In Active Markets for Identical Assets/Liabilities (Level 1) | Other | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 0 0  
Pension | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 2,147 1,834  
Pension | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Other Observable Inputs (Level 2) | U.S. securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Other Observable Inputs (Level 2) | International securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Other Observable Inputs (Level 2) | Investment Funds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 2,072 1,757  
Pension | Significant Other Observable Inputs (Level 2) | Government bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 72 72  
Pension | Significant Other Observable Inputs (Level 2) | Corporate bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Other Observable Inputs (Level 2) | Other | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 3 5  
Pension | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 28 32  
Pension | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | U.S. securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | International securities | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | Investment Funds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | Government bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | Corporate bonds | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets  
Pension | Significant Unobservable Inputs (Level 3) | Other | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets 28 32  
Pension | Fair Value Measured at Net Asset Value Per Share | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Total assets $ 283 $ 272