Stockholders' Equity - Company's Restricted Stock Grants and Stock Options (Detail)	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Options unvested, beginning balance | shares	271,700,000
Options granted | shares	214,500,000
Options unvested, ending balance | shares	486,200,000
Quantity ending exercisable balance | shares	66,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, Options unvested, beginning balance | $ / shares	$ 30.65
Weighted-average grant date fair value, Options granted | $ / shares	34.78
Weighted-average grant date fair value, Options unvested, ending balance | $ / shares	32.47
Weighted-average grant date fair value, Quantity ending exercisable balance | $ / shares	$ 30.65
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares unvested, beginning balance | shares	786,300,000
Shares granted | shares	325,600,000
Shares for which restrictions lapsed | shares	(175,100,000)
Shares unvested, ending balance | shares	936,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, beginning balance | $ / shares	$ 35.69
Weighted-average grant date fair value, shares granted | $ / shares	34.58
Weighted-average grant date fair value, shares for which restrictions lapsed | $ / shares	38.06
Weighted-average grant date fair value, ending balance | $ / shares	$ 34.93