Financial Instruments - Long-Term Debt, New Issuances (Details) $ in Millions	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Principal amount	$ 4,000	[1]
Senior Notes [Member] | Senior Unsecured Debt, Zero Point Eight Zero Zero Percent, Due 2025 [Member]
Debt Instrument [Line Items]
Stated interest rate	0.80%	[1]
Principal amount	$ 750	[1]
Senior Notes [Member] | Senior Unsecured Debt, One Point Seven Zero Zero Percent, Due 2030 [Member]
Debt Instrument [Line Items]
Stated interest rate	1.70%	[1]
Principal amount	$ 1,000	[1]
Senior Notes [Member] | Senior Unsecured Debt, Two Point Five Five Zero Percent, Due 2040 [Member]
Debt Instrument [Line Items]
Stated interest rate	2.55%	[1]
Principal amount	$ 1,000	[1]
Senior Notes [Member] | Senior Unsecured Debt, Two Point Seven Zero Zero Percent, Due 2050 [Member]
Debt Instrument [Line Items]
Stated interest rate	2.70%	[1]
Principal amount	$ 1,250	[1]
Senior Notes [Member] | Senior Unsecured Debt, Two Point Six Two Five Percent, Due 2030 [Member]
Debt Instrument [Line Items]
Stated interest rate	2.625%	[2]
Principal amount	$ 1,250	[2]

[1] May be redeemed by us at any time, in whole, or in part, at varying redemption prices plus accrued and unpaid interest. The weighted-average effective interest rate for the notes at issuance was 2.11%.

[2] May be redeemed by us at any time, in whole, or in part, at a redemption price plus accrued and unpaid interest. The weighted average effective interest rate for the notes at issuance was 2.67%.