v3.20.2
Overview - Additional Information (Detail)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 09, 2020
USD ($)
shares
Sep. 01, 2020
USD ($)
Aug. 10, 2020
Feb. 19, 2020
USD ($)
shares
Sep. 30, 2020
USD ($)
shares
Sep. 30, 2020
USD ($)
Segment
shares
Sep. 30, 2019
USD ($)
Schedule Of Organization Consolidation And Presentation Of Financial Statements [Line Items]              
Number of operating segment | Segment           2  
Number of reportable segment | Segment           2  
Number of shares issued in public offering | shares       15,200,000      
Stock split ratio     5     5 5
Stock split, dividend description           five-for-one stock split effected in the form of a stock dividend in August 2020  
Proceeds from issuances of common stock in public offerings, net of issuance costs       $ 2,310   $ 7,282 $ 848
Common stock public offering issuance costs       $ 28      
At-the-Market Offering Program [Member]              
Schedule Of Organization Consolidation And Presentation Of Financial Statements [Line Items]              
Common stock public offering issuance costs         $ 26 26  
Common stock issuance value         $ 4,973 $ 4,973  
At-the-Market Offering Program [Member] | Common Stock [Member]              
Schedule Of Organization Consolidation And Presentation Of Financial Statements [Line Items]              
Number of shares issued in public offering | shares [1]         11,000,000 11,000,000  
Proceeds from issuances of common stock in public offerings, net of issuance costs $ 5,000            
Common stock issuance value   $ 5,000     $ 0 [1] $ 0 [1]  
Sale of common stock, number of shares | shares 11,141,562            
Net proceeds from Issuance of common stock $ 4,970            
Sales agents’ commissions 25            
Other offering costs $ 1            
[1] Prior period results have been adjusted to reflect the five-for-one stock split effected in the form of a stock dividend in August 2020. See Note 1, Overview for details.