Fair Value Measurement - Financial Instruments Carried at Fair Value (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | | | | |
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Mar. 31, 2020 | Dec. 31, 2019 | Mar. 31, 2019 | Dec. 31, 2018 |
Current Assets | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | $ 1 | $ 8 | $ 1 | $ 8 | $ 8 | $ 4 | $ 5 | $ 14 |
Net realized and unrealized gains (losses) included in earnings | (7) | 10 | 0 | 8 | | | | |
Transfers out of Level 3 | 0 | (6) | | (8) | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | 0 | 1 | (3) | (6) | | | | |
Net unrealized gains (losses) on derivatives still held included in earnings | (3) | 7 | 1 | 7 | | | | |
Current Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 98 | | 98 | | | 32 | | |
Long- Term Assets | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | 0 | 2 | 0 | 2 | 1 | 0 | 1 | 2 |
Net realized and unrealized gains (losses) included in earnings | 0 | 1 | 0 | 2 | | | | |
Transfers out of Level 3 | 1 | 0 | | (2) | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | 0 | 0 | 0 | 0 | | | | |
Net unrealized gains (losses) on derivatives still held included in earnings | 0 | 1 | 0 | 1 | | | | |
Long- Term Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 29 | | 29 | | | 2 | | |
Long- Term Assets | Equity Securities [Member] | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Restricted Investments, at Fair Value | 6 | | 6 | | | 0 | | |
Current Liabilities | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | (3) | (1) | (3) | (1) | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value | (3) | (1) | (3) | (1) | 3 | (1) | 1 | 0 |
Net realized and unrealized (losses) gains included in earnings | 2 | 1 | 6 | (1) | | | | |
Transfers out of Level 3 | 0 | | | | | | | |
Transfers out of Level 3 | | 0 | | 0 | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | 2 | 1 | | | | | | |
Settlements | | | (8) | 0 | | | | |
Net unrealized gains (losses) on derivatives still held included in earnings | (1) | 0 | (2) | (1) | | | | |
Current Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 66 | | 66 | | | 58 | | |
Long- Term Liabilities | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | (4) | 0 | (4) | 0 | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value | (4) | 0 | (4) | 0 | $ 1 | (3) | $ 1 | $ (2) |
Net realized and unrealized (losses) gains included in earnings | (3) | 1 | (1) | 1 | | | | |
Transfers out of Level 3 | 0 | | | | | | | |
Transfers out of Level 3 | | 0 | | 1 | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | 0 | 0 | | | | | | |
Settlements | | | 0 | 0 | | | | |
Net unrealized gains (losses) on derivatives still held included in earnings | (3) | $ 0 | 1 | $ 0 | | | | |
Long- Term Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 37 | | 37 | | | 20 | | |
Level 1 | Current Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 74 | | 74 | | | 13 | | |
Level 1 | Long- Term Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 24 | | 24 | | | 1 | | |
Level 1 | Long- Term Assets | Equity Securities [Member] | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Restricted Investments, at Fair Value | 6 | | 6 | | | 0 | | |
Level 1 | Current Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 41 | | 41 | | | 15 | | |
Level 1 | Long- Term Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 17 | | 17 | | | 2 | | |
Level 2 | Current Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 23 | | 23 | | | 15 | | |
Level 2 | Long- Term Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 5 | | 5 | | | 1 | | |
Level 2 | Long- Term Assets | Equity Securities [Member] | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Restricted Investments, at Fair Value | 0 | | 0 | | | 0 | | |
Level 2 | Current Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 22 | | 22 | | | 42 | | |
Level 2 | Long- Term Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 16 | | 16 | | | 15 | | |
Level 3 | Current Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 1 | | 1 | | | 4 | | |
Level 3 | Long- Term Assets | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - assets | 0 | | 0 | | | 0 | | |
Level 3 | Long- Term Assets | Equity Securities [Member] | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Restricted Investments, at Fair Value | 0 | | 0 | | | 0 | | |
Level 3 | Current Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | 3 | | 3 | | | 1 | | |
Level 3 | Long- Term Liabilities | Commodity derivatives | | | | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | | | | |
Commodity derivatives - liabilities | $ 4 | | $ 4 | | | $ (3) | | |