Long-term Debt and Debt Facility Agreements - Long-term Debt (Detail) $ in Millions, € in Billions	Dec. 31, 2020 USD ($)	Jun. 30, 2020 EUR (€)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 16,036	€ 5.0	$ 14,770
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,496		1,495
3.90% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,450		1,444
1.375% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,221
2.40% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	999		998
2.0% Guaranteed Notes due 2032
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,214
4.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	930		929
4.30% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term debt, carrying amount	846		845
0.50% Notes due 2031
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,099		544
3.75% Senior Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	746		746
2.65% Senior Notes due 2030
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,250
1.00% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	736		665
2.65% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	598		598
1.40% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	498
0.25% Notes due 2027
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,100		550
3.63% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	295		294
7.00% Notes due 2038
Debt Instrument [Line Items]
Long-term debt, carrying amount	206		208
5.95% Notes due 2041
Debt Instrument [Line Items]
Long-term debt, carrying amount	114		114
5.13% Notes due 2043
Debt Instrument [Line Items]
Long-term debt, carrying amount	99		99
0.00% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	611		551
4.00% Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	80		81
3.70% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	55		55
3.30% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount			1,597
4.20% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount			600
Other
Debt Instrument [Line Items]
Long-term debt, carrying amount			135
Commercial paper borrowings
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 393		$ 2,222