Stockholders' Equity - Narrative (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Oct. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock in public offering of common stock (in shares)	2,587,500
Issuance of common stock in public offering of common stock	$ 1,700,000,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, approved (in shares)				735,818
Weighted-average grant date fair value (in dollars per share)				$ 671.89
Service period (in years)				3 years 7 months 6 days
2020 ATM Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of stock, equity offering agreement, authorized						$ 1,500,000,000
Issuance of common stock in public offering of common stock (in shares)		0	252,982	137,604	415,512
Issuance of common stock in public offering of common stock			$ 196,500,000	$ 99,600,000	$ 298,300,000
Sale of stock, equity offering agreement, available for sale		$ 1,400,000,000		$ 1,400,000,000