Income Taxes - Income Tax Expense (Benefit) Table (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 269	$ 147	$ 437	$ 237
Deferred income tax expense (benefit)	(60)	(22)	(62)	14
Total income tax expense (benefit)	209	125	375	251
Income (loss) before income taxes	$ (736)	$ 142	$ (474)	$ 442
Effective tax rate	(28.00%)	88.00%	(79.00%)	57.00%

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

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Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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