Income Taxes - Quarter information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Income Taxes
Effective tax rate of income (loss) before income taxes	17.00%	24.80%
Excess tax benefits associated with equity-based compensation	$ 21	$ 13
Equity in net losses of unconsolidated entities	26	9
Investment impairment		52
Investments Qualifying for Federal Tax Credits [Member]
Income Taxes
Equity in net losses of unconsolidated entities	26	9
Income tax (expense) benefit, including tax credits, from equity method investment	24	15
Interest expense	3	$ 2
Refined Coal Facility [Member]
Income Taxes
Equity method investments impairment charges	$ 7

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Amount of the cost of borrowed funds accounted for as interest expense.

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Income tax expense (benefit), including federal tax credits, from equity method investment.

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Income Taxes [Line Items]

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The amount by which the fair value of an investment is less than the carrying amount of that investment and the decline in fair value is deemed to be other than temporary.

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