Share-based Compensation - Summary of Stock Option Plan Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Granted	0
Time Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Outstanding beginning	4,631,836	5,869,303	8,158,168
Number of Options, Granted		750,000	1,000
Number of Options, Forfeited	(662,732)	(988,826)	(996,015)
Number of Options, Expired	(445,760)	(153,799)
Number of Options, Exercised	(9,027)	(844,842)	(1,293,850)
Number of Options, Outstanding ending	3,514,317	4,631,836	5,869,303	8,158,168
Number of Options, Exercisable	2,817,876
Weighted-Average Exercise Price, Outstanding beginning	$ 43.20	$ 41.58	$ 40.19
Weighted-Average Exercise Price, Granted		40.00	36.17
Weighted-Average Exercise Price, Forfeited	46.31	46.08	47.59
Weighted-Average Exercise Price, Expired	28.09	30.47
Weighted-Average Exercise Price, Exercised	17.44	28.04	28.13
Weighted-Average Exercise Price, Outstanding ending	44.60	$ 43.20	$ 41.58	$ 40.19
Weighted-Average Exercise Price, Exercisable	$ 44.77
Weighted Average Remaining Contractual Term in Years	3 years 1 month 24 days	3 years 7 months 28 days	3 years 6 months 7 days	4 years 5 months 4 days
Weighted Average Remaining Contractual Term in Years, Exercisable	2 years 7 months 9 days
Aggregate Intrinsic Value			$ 13	$ 43

Outstanding options weighted average remaining contractual term.

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Share based compensation arrangement by share based awards options exercisable weighted average remaining contractual term.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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