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Long-Term Debt - Additional Information (Detail) - USD ($)
$ in Millions
Mar. 18, 2021
Jun. 30, 2021
Dec. 31, 2020
Debt Instrument [Line Items]      
Long-term debt   $ 3,385 $ 2,872
Estimated fair value   $ 4,035 $ 3,597
2.40% Notes [Member]      
Debt Instrument [Line Items]      
Debt instrument, maturity year 2031    
Aggregate principal amount issued $ 400    
Stated interest rate 2.40%    
Debt instrument maturity date Mar. 15, 2031    
Redeemable principal amount percentage 100.00%    
Basis spread on federal funds rate 0.15%    
Redeemable principal amount percentage 100.00%    
Debt instrument, start date of redemption Dec. 15, 2030    
Debt instrument, offering date Mar. 18, 2021    
3.45% Notes [Member]      
Debt Instrument [Line Items]      
Debt instrument, maturity year 2051    
Aggregate principal amount issued $ 400    
Stated interest rate 3.45%    
Debt instrument maturity date Mar. 15, 2051    
Redeemable principal amount percentage 100.00%    
Basis spread on federal funds rate 0.20%    
Redeemable principal amount percentage 100.00%    
Debt instrument, start date of redemption Sep. 15, 2050    
Debt instrument, offering date Mar. 18, 2021