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Debt - Borrowings and Repayments (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	May 31, 2021	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Nov. 30, 2020
Debt
New borrowings			$ 1,707
Premiums paid on early extinguishment of debt			211
Loss on early extinguishment of debt, net		$ (220)	(220)
Debt repayments			2,326	$ 705
Non-cash financing lease incurred			32
Commercial Paper Program [Member]
Debt
Commercial paper repayments			954
Commercial paper borrowings			640
Senior Notes, Aggregate [Member]
Debt
Debt instrument face amount	$ 950				$ 2,500
New borrowings	942
Early extinguishment of debt	1,289
Premiums paid on early extinguishment of debt	211
Loss on early extinguishment of debt, net	(220)
Accrued interest	15
Principal amount outstanding	5,965
Senior Notes, Aggregate [Member] \| Cash Flow Hedging [Member]
Debt
Interest expense	6
2.00% senior notes due June 1, 2029 [Member]
Debt
Debt instrument face amount	$ 475
Interest rate (as a percent)	2.00%
2.95% senior notes due June 1, 2041 [Member]
Debt
Debt instrument face amount	$ 475
Interest rate (as a percent)	2.95%
6.125% senior notes due 2039 [Member]
Debt
Interest rate (as a percent)	6.125%
Early extinguishment of debt	$ 6
Principal amount outstanding	$ 252
7.75% senior notes due 2032 [Member]
Debt
Interest rate (as a percent)	7.75%
Early extinguishment of debt	$ 9
Principal amount outstanding	$ 153
7.375% senior notes due 2029 [Member]
Debt
Interest rate (as a percent)	7.375%
Principal amount outstanding	$ 81
4.15% senior notes due 2049 [Member]
Debt
Interest rate (as a percent)	4.15%
Early extinguishment of debt	$ 316
Principal amount outstanding	$ 1,000
4.10% senior notes due 2045 [Member]
Debt
Interest rate (as a percent)	4.10%
Early extinguishment of debt	$ 334
Principal amount outstanding	$ 750
3.90% senior notes due 2035 [Member]
Debt
Interest rate (as a percent)	3.90%
Early extinguishment of debt	$ 153
Principal amount outstanding	$ 450
7.00% senior notes due 2028 [Member]
Debt
Interest rate (as a percent)	7.00%
Early extinguishment of debt	$ 73
Principal amount outstanding	$ 330
7.10% senior notes due 2026 [Member]
Debt
Interest rate (as a percent)	7.10%
Early extinguishment of debt	$ 26
Principal amount outstanding	$ 249
3.50% senior notes due 2024 [Member]
Debt
Interest rate (as a percent)	3.50%
Early extinguishment of debt	$ 194
Principal amount outstanding	$ 350
3.125% senior notes due 2025 [Member]
Debt
Interest rate (as a percent)	3.125%
Early extinguishment of debt	$ 178
Principal amount outstanding	$ 600
3.15% senior notes due 2027 [Member]
Debt
Interest rate (as a percent)	3.15%
Principal amount outstanding	$ 750
2.90% senior notes due 2022 [Member]
Debt
Interest rate (as a percent)	2.90%
Principal amount outstanding	$ 500
2.40% senior notes due 2023 [Member]
Debt
Interest rate (as a percent)	2.40%
Principal amount outstanding	$ 500
Tax Exempt Bonds [Member]
Debt
New borrowings			125
Debt repayments			24
Financing leases and other [Member]
Debt
Debt repayments			$ 59
Treasury rate lock [Member] \| Senior Notes, Aggregate [Member]
Debt
Derivative notional value	450
Derivative payment	$ 8