Income Taxes - Quarter information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Taxes
Effective tax rate of income (loss) before income taxes	23.70%	24.50%		23.20%	21.40%
Excess tax benefits associated with equity-based compensation	$ 5	$ 2		$ 16	$ 25
Equity in net losses of unconsolidated entities	14	16		34	56
Increase (decrease) to accruals and related deferred taxes	10			10	(6)
Nondeductible acquisition transaction costs		19
Investments Qualifying for Federal Tax Credits [Member]
Income Taxes
Equity in net losses of unconsolidated entities	15	16		36	59
Income tax (expense) benefit, including tax credits, from equity method investment	21	24		53	65
Interest expense	$ 2	$ 3		$ 7	9
Refined Coal Facility [Member]
Income Taxes
Equity method investments impairment charges			$ 7		$ 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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The increase (decrease) during the period in the amount due for taxes based on the reporting entity's earnings or attributable to the entity's income earning process (business presence) within a given jurisdiction.

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

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to nondeductible acquisition transaction costs.

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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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