Stock-based Compensation Plans - Summary of Stock Option Activity (Detail) - $ / shares shares in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning of year, Shares	43,529	47,210	46,502
Granted, Shares	5,604	2,121	5,024
Exercised, Shares	(1,045)	(936)	(1,156)
Forfeited, Shares	(1,819)	(4,866)	(3,160)
Outstanding at year-end, Shares	46,269	43,529	47,210
Outstanding at beginning of year, Weighted-Average Exercise Price	$ 79.36	$ 79.13	$ 78.31
Granted, Weighted-Average Exercise Price	41.50	76.95	86.55
Exercised, Weighted-Average Exercise Price	38.50	54.20	57.87
Forfeited, Weighted-Average Exercise Price	74.69	84.19	86.99
Outstanding at year-end, Weighted-Average Exercise Price	$ 75.65	$ 79.36	$ 79.13

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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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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 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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Number of share options (or share units) exercised during the current period.

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