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Recent Accounting Pronouncements - Summary Of Information About In Adoption Of ASU 2019-12 (Detail) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Jun. 30, 2019 | Sep. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |
Provision (benefit) for income taxes |  |  |  |  |  | $ 2 | $ 0 | $ 944
Net income (loss) |  |  |  |  |  | $ (359) | $ (296) | $ (1,605)
Earnings Per Share [Abstract] |  |  |  |  |  |  |  |
Basic |  |  |  |  |  | $ (4.43) | $ (3.33) | $ (13.50)
Diluted |  |  |  |  |  | $ (4.43) | $ (3.33) | $ (13.50)
Previously Reported [Member] | Accounting Standards Update 2019-12 [Member] |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |
Provision (benefit) for income taxes | $ 18 | $ (37) | $ (2) | $ (39) | $ (21) |  |  |
Net income (loss) | $ 71 | $ (170) | $ (17) | $ (187) | $ (116) |  |  |
Earnings Per Share [Abstract] |  |  |  |  |  |  |  |
Basic | $ 0.86 | $ (2.02) | $ (0.20) | $ (2.20) | $ (1.40) |  |  |
Diluted | $ 0.86 | $ (2.02) | $ (0.20) | $ (2.20) | $ (1.40) |  |  |
Revised [Member] | Accounting Standards Update 2019-12 [Member] |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |
Provision (benefit) for income taxes | $ 6 | $ 0 | $ 2 | $ 2 | $ 8 |  |  |
Net income (loss) | $ 83 | $ (207) | $ (21) | $ (228) | $ (145) |  |  |
Earnings Per Share [Abstract] |  |  |  |  |  |  |  |
Basic | $ 1.00 | $ (2.45) | $ (0.24) | $ (2.68) | $ (1.75) |  |  |
Diluted | $ 1.00 | $ (2.45) | $ (0.24) | $ (2.68) | $ (1.75) |  |  |

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