Borrowings and Credit Arrangements - Schedule of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2020	Aug. 31, 2020	Dec. 31, 2019	Aug. 31, 2019	Aug. 15, 2019
Debt Instrument [Line Items]
Long-term debt	$ 64,235
Finance lease liabilities	1,083		$ 808
Total debt principal	65,318		69,246
Debt premiums	238		262
Debt discounts and deferred financing costs	(909)		(1,028)
Long-term debt and lease obligations	64,647		68,480
Current portion of long-term debt	(5,440)		(3,781)
Long-term debt	$ 59,207		64,699
Senior Notes | 3.125% senior notes due March 2020
Debt Instrument [Line Items]
Debt interest rate	3.125%			3.125%
Long-term debt	$ 0		723
Senior Notes | 2.8% senior notes due July 2020
Debt Instrument [Line Items]
Debt interest rate	2.80%
Long-term debt	$ 0		2,750
Senior Notes | 3.35% senior notes due March 2021
Debt Instrument [Line Items]
Debt interest rate	3.35%			3.35%
Long-term debt	$ 2,038		2,038
Senior Notes | 4.125% senior notes due May 2021
Debt Instrument [Line Items]
Debt interest rate	4.125%			4.125%
Long-term debt	$ 222		222
Senior Notes | 2.125% senior notes due June 2021
Debt Instrument [Line Items]
Debt interest rate	2.125%
Long-term debt	$ 1,750		1,750
Senior Notes | 4.125% senior notes due June 2021
Debt Instrument [Line Items]
Debt interest rate	4.125%			4.125%
Long-term debt	$ 203		203
Senior Notes | 5.45% senior notes due June 2021
Debt Instrument [Line Items]
Debt interest rate	5.45%			5.45%
Long-term debt	$ 187		187
Senior Notes | 3.5% senior notes due July 2022
Debt Instrument [Line Items]
Debt interest rate	3.50%
Long-term debt	$ 1,500		1,500
Senior Notes | 2.75% senior notes due November 2022
Debt Instrument [Line Items]
Debt interest rate	2.75%
Long-term debt	$ 1,000		1,000
Senior Notes | 2.75% senior notes due December 2022
Debt Instrument [Line Items]
Debt interest rate	2.75%
Long-term debt	$ 1,250		1,250
Senior Notes | 4.75% senior notes due December 2022
Debt Instrument [Line Items]
Debt interest rate	4.75%
Long-term debt	$ 399		399
Senior Notes | 3.7% senior notes due March 2023
Debt Instrument [Line Items]
Debt interest rate	3.70%	3.70%
Long-term debt	$ 2,336		6,000
Senior Notes | 2.8% senior notes due June 2023
Debt Instrument [Line Items]
Debt interest rate	2.80%
Long-term debt	$ 1,300		1,300
Senior Notes | 4% senior notes due December 2023
Debt Instrument [Line Items]
Debt interest rate	4.00%	4.00%
Long-term debt	$ 414		1,250
Senior Notes | 3.375% senior notes due August 2024
Debt Instrument [Line Items]
Debt interest rate	3.375%
Long-term debt	$ 650		650
Senior Notes | 2.625% senior notes due August 2024
Debt Instrument [Line Items]
Debt interest rate	2.625%				2.625%
Long-term debt	$ 1,000		1,000
Senior Notes | 3.5% senior notes due November 2024
Debt Instrument [Line Items]
Debt interest rate	3.50%
Long-term debt	$ 750		750
Senior Notes | 5% senior notes due December 2024
Debt Instrument [Line Items]
Debt interest rate	5.00%
Long-term debt	$ 299		299
Senior Notes | 4.1% senior notes due March 2025
Debt Instrument [Line Items]
Debt interest rate	4.10%	4.10%
Long-term debt	$ 950		5,000
Senior Notes | 3.875% senior notes due July 2025
Debt Instrument [Line Items]
Debt interest rate	3.875%
Long-term debt	$ 2,828		2,828
Senior Notes | 2.875% senior notes due June 2026
Debt Instrument [Line Items]
Debt interest rate	2.875%
Long-term debt	$ 1,750		1,750
Senior Notes | 3% senior notes due August 2026
Debt Instrument [Line Items]
Debt interest rate	3.00%				3.00%
Long-term debt	$ 750		750
Senior Notes | 3.625% senior notes due April 2027
Debt Instrument [Line Items]
Debt interest rate	3.625%
Long-term debt	$ 750		0
Senior Notes | 6.25% senior notes due June 2027
Debt Instrument [Line Items]
Debt interest rate	6.25%
Long-term debt	$ 372		372
Senior Notes | 1.3% senior notes due August 2027
Debt Instrument [Line Items]
Debt interest rate	1.30%
Long-term debt	$ 2,250		0
Senior Notes | 4.3% senior notes due March 2028
Debt Instrument [Line Items]
Debt interest rate	4.30%
Long-term debt	$ 7,050		9,000
Senior Notes | 3.25% senior notes due August 2029
Debt Instrument [Line Items]
Debt interest rate	3.25%				3.25%
Long-term debt	$ 1,750		1,750
Senior Notes | 3.75% senior notes due April 2030
Debt Instrument [Line Items]
Debt interest rate	3.75%
Long-term debt	$ 1,500		0
Senior Notes | 1.75% senior notes due August 2030
Debt Instrument [Line Items]
Debt interest rate	1.75%
Long-term debt	$ 1,250		0
Senior Notes | 1.875% senior notes due February 2031
Debt Instrument [Line Items]
Debt interest rate	1.875%
Long-term debt	$ 1,250		0
Senior Notes | 4.875% senior notes due July 2035
Debt Instrument [Line Items]
Debt interest rate	4.875%
Long-term debt	$ 652		652
Senior Notes | 6.625% senior notes due June 2036
Debt Instrument [Line Items]
Debt interest rate	6.625%
Long-term debt	$ 771		771
Senior Notes | 6.75% senior notes due December 2037
Debt Instrument [Line Items]
Debt interest rate	6.75%
Long-term debt	$ 533		533
Senior Notes | 4.78% senior notes due March 2038
Debt Instrument [Line Items]
Debt interest rate	4.78%
Long-term debt	$ 5,000		5,000
Senior Notes | 6.125% senior notes due September 2039
Debt Instrument [Line Items]
Debt interest rate	6.125%
Long-term debt	$ 447		447
Senior Notes | 4.125% senior notes due April 2040
Debt Instrument [Line Items]
Debt interest rate	4.125%
Long-term debt	$ 1,000		0
Senior Notes | 2.7% senior notes due August 2040
Debt Instrument [Line Items]
Debt interest rate	2.70%
Long-term debt	$ 1,250		0
Senior Notes | 5.75% senior notes due May 2041
Debt Instrument [Line Items]
Debt interest rate	5.75%
Long-term debt	$ 133		133
Senior Notes | 4.5% senior notes due May 2042
Debt Instrument [Line Items]
Debt interest rate	4.50%
Long-term debt	$ 500		500
Senior Notes | 4.125% senior notes due November 2042
Debt Instrument [Line Items]
Debt interest rate	4.125%
Long-term debt	$ 500		500
Senior Notes | 5.3% senior notes due December 2043
Debt Instrument [Line Items]
Debt interest rate	5.30%
Long-term debt	$ 750		750
Senior Notes | 4.75% senior notes due March 2044
Debt Instrument [Line Items]
Debt interest rate	4.75%
Long-term debt	$ 375		375
Senior Notes | 5.125% senior notes due July 2045
Debt Instrument [Line Items]
Debt interest rate	5.125%
Long-term debt	$ 3,500		3,500
Senior Notes | 3.875% senior notes due August 2047
Debt Instrument [Line Items]
Debt interest rate	3.875%
Long-term debt	$ 1,000		1,000
Senior Notes | 5.05% senior notes due March 2048
Debt Instrument [Line Items]
Debt interest rate	5.05%
Long-term debt	$ 8,000		8,000
Senior Notes | 4.25% senior notes due April 2050
Debt Instrument [Line Items]
Debt interest rate	4.25%
Long-term debt	$ 750		$ 0
Notes Payable | Floating rate notes due March 2020
Debt Instrument [Line Items]
Debt interest rate			2.515%
Long-term debt	$ 0		$ 277
Notes Payable | Floating rate notes due March 2021
Debt Instrument [Line Items]
Debt interest rate	0.95%		2.605%
Long-term debt	$ 1,000		$ 1,000
Other Debt Obligations
Debt Instrument [Line Items]
Long-term debt	$ 326		$ 279