Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 2
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Share-based compensation actual payout as a percentage of the target.

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Share-based compensation potential payout as a percentage of the target.

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Equity-Based Compensation - PSUs (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 29, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years	3 years
Potential payout (as a percent)		100.00%
Shares issued under the plan	476,000
Unvested, Units, beginning of year		1,077
Granted, Units		301
Vested, Units	(715,000)	(362)
Forfeited, Units		(17)
Unvested, Units, end of year		999	1,077
Unvested, Weighted Average Per Share Fair Value, beginning of year		$ 99.66
Granted, Weighted Average Per Share Fair Value		153.34
Vested, Weighted Average Per Share Fair Value		84.54
Forfeited, Weighted Average Per Share Fair Value		121.81
Unvested, Weighted Average Per Share Fair Value, end of year		$ 120.95	$ 99.66
Total fair market value of vested awards		$ 89	$ 84	$ 78
Total Shareholder Return Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout (as a percent)			194.70%
Cash Flow Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout (as a percent)			200.00%
Deferred Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards outstanding (in shares)		197,000
Minimum [Member] \| Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential payout (as a percent)		0.00%
Maximum [Member] \| Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential payout (as a percent)		200.00%