Common Stock - Summary of Information and Changes in Stock Options with Regard to Stock Option Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares under stock option, Beginning of the year	21,310,099	21,009,508	22,472,047
Number of Shares Granted	1,650,262	1,493,576	1,610,599
Number of Shares Forfeited	(1,954,859)	(944,917)	(1,318,380)
Number of Shares Exercised		(248,068)	(1,754,758)
Number of shares under stock option, End of the year	21,005,502	21,310,099	21,009,508	22,472,047
Number of stock options, Exercisable	17,893,434	17,796,607	15,223,029
Weighted Average Exercise Price, Beginning of year	$ 47.68	$ 48.88	$ 48.99
Weighted Average Exercise Price, Stock Options Granted	20.23	28.72	35.09
Weighted Average Exercise Price, Stock Options Forfeited	45.75	50.57	57.56
Weighted Average Exercise Price, Stock Options Exercised		29.70	44.12
Weighted Average Exercise Price, End of the year	45.70	47.68	48.88	$ 48.99
Weighted Average Exercise Price, Stock Options, Exercisable	$ 49.25	$ 50.49	$ 54.13
Weighted Average Remaining Contractual Term, Outstanding	4 years 10 months 20 days			5 years 4 months 9 days
Weighted Average Remaining Contractual Term, Exercisable	4 years 3 months 10 days