Fair Value Measurements (Schedule Of Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Millions | Jun. 30, 2020 | Dec. 31, 2019 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Net, Current | $ 347 | $ 148 |
Risk Management Assets, Net, Long-term | 2 | 2 |
Risk Management Liabilities, Net, Current | 55 | 114 |
Risk Management Liabilities, Net, Long-term | 109 | 68 |
Guarantor Obligations, Current Carrying Value | 11 | 9 |
Other Liabilities and Provisions [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 9 | 7 |
Other Liabilities and Provisions [Member] | Carrying Amount [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 9 | 7 |
Other Liabilities and Provisions [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 0 | 0 |
Other Liabilities and Provisions [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 9 | 7 |
Other Liabilities and Provisions [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 0 | 0 |
Accounts Payable and Accrued Liabilities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 2 | 2 |
Accounts Payable and Accrued Liabilities [Member] | Carrying Amount [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 2 | 2 |
Accounts Payable and Accrued Liabilities [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 0 | 0 |
Accounts Payable and Accrued Liabilities [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 2 | 2 |
Accounts Payable and Accrued Liabilities [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Guarantor Obligations, Current Carrying Value | 0 | 0 |
Commodity Derivatives [Member] | Other Current Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 496 | 202 |
Risk Management Assets, Gross Liabilities | (149) | (67) |
Risk Management Assets, Net, Current | 347 | 135 |
Commodity Derivatives [Member] | Other Current Assets [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 2 | 0 |
Commodity Derivatives [Member] | Other Current Assets [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 411 | 202 |
Commodity Derivatives [Member] | Other Current Assets [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 83 | 0 |
Commodity Derivatives [Member] | Other Noncurrent Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 4 | 6 |
Risk Management Assets, Gross Liabilities | (4) | (4) |
Risk Management Assets, Net, Long-term | 0 | 2 |
Commodity Derivatives [Member] | Other Noncurrent Assets [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 0 | 0 |
Commodity Derivatives [Member] | Other Noncurrent Assets [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 4 | 6 |
Commodity Derivatives [Member] | Other Noncurrent Assets [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 0 | 0 |
Commodity Derivatives [Member] | Other Current Liabilities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 200 | 181 |
Risk Management Liabilities, Gross Assets | (149) | (67) |
Risk Management Liabilities, Net, Current | 51 | 114 |
Commodity Derivatives [Member] | Other Current Liabilities [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | 1 |
Commodity Derivatives [Member] | Other Current Liabilities [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 200 | 139 |
Commodity Derivatives [Member] | Other Current Liabilities [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | 41 |
Commodity Derivatives [Member] | Other Liabilities and Provisions [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 112 | 72 |
Risk Management Liabilities, Gross Assets | (4) | (4) |
Risk Management Liabilities, Net, Long-term | 108 | 68 |
Commodity Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | 0 |
Commodity Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 110 | 61 |
Commodity Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 2 | 11 |
Foreign Currency Derivatives [Member] | Other Current Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | | 13 |
Risk Management Assets, Gross Liabilities | | 0 |
Risk Management Assets, Net, Current | | 13 |
Foreign Currency Derivatives [Member] | Other Current Assets [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | | 0 |
Foreign Currency Derivatives [Member] | Other Current Assets [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | | 13 |
Foreign Currency Derivatives [Member] | Other Current Assets [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | | $ 0 |
Foreign Currency Derivatives [Member] | Other Noncurrent Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 2 | |
Risk Management Assets, Gross Liabilities | 0 | |
Risk Management Assets, Net, Long-term | 2 | |
Foreign Currency Derivatives [Member] | Other Noncurrent Assets [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 0 | |
Foreign Currency Derivatives [Member] | Other Noncurrent Assets [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 2 | |
Foreign Currency Derivatives [Member] | Other Noncurrent Assets [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Assets, Gross assets | 0 | |
Foreign Currency Derivatives [Member] | Other Current Liabilities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 4 | |
Risk Management Liabilities, Gross Assets | 0 | |
Risk Management Liabilities, Net, Current | 4 | |
Foreign Currency Derivatives [Member] | Other Current Liabilities [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | |
Foreign Currency Derivatives [Member] | Other Current Liabilities [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 4 | |
Foreign Currency Derivatives [Member] | Other Current Liabilities [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | |
Foreign Currency Derivatives [Member] | Other Liabilities and Provisions [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 1 | |
Risk Management Liabilities, Gross Assets | 0 | |
Risk Management Liabilities, Net, Long-term | 1 | |
Foreign Currency Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 0 | |
Foreign Currency Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | 1 | |
Foreign Currency Derivatives [Member] | Other Liabilities and Provisions [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Risk Management Liabilities, Gross liabilities | $ 0 | |