Borrowings - Schedule of Borrowings (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Finance lease obligations	$ 1,002		$ 808
Total debt principal	72,438		69,246
Debt premiums	251		262
Debt discounts and deferred financing costs	(1,016)		(1,028)
Long-term debt and lease obligation	71,673		68,480
Current portion of long-term debt	(8,192)		(3,781)
Long-term debt	63,481		$ 64,699
Senior Notes | 3.125% senior notes due March 2020
Debt Instrument [Line Items]
Debt interest rate			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	$ 2,750		2,750
Senior Notes | 3.35% senior notes due March 2021
Debt Instrument [Line Items]
Debt interest rate	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%
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%
Long-term debt	$ 203		203
Senior Notes | 5.45% senior notes due June 2021
Debt Instrument [Line Items]
Debt interest rate	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%
Long-term debt	$ 6,000		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%
Long-term debt	$ 1,250		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	2.265%
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%
Long-term debt	$ 5,000		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%
Long-term debt	$ 750		750
Senior Notes | 3.625% senior notes due April 2027
Debt Instrument [Line Items]
Debt interest rate	3.625%	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 | 4.3% senior notes due March 2028
Debt Instrument [Line Items]
Debt interest rate	4.30%
Long-term debt	$ 9,000		9,000
Senior Notes | 3.25% senior notes due August 2029
Debt Instrument [Line Items]
Debt interest rate	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%	3.75%
Long-term debt	$ 1,500		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%	4.125%
Long-term debt	$ 1,000		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%	4.25%
Long-term debt	$ 750		$ 0
Floating Rate Notes | Floating rate notes due March 2020 (2.515% at December 31, 2019)
Debt Instrument [Line Items]
Debt interest rate			2.515%
Long-term debt	$ 0		$ 277
Floating Rate Notes | Floating rate notes due March 2021 (1.033% at June 30, 2020 and 2.605% at December 31, 2019)
Debt Instrument [Line Items]
Debt interest rate	1.033%		2.605%
Long-term debt	$ 1,000		$ 1,000
Other Debt Obligations
Debt Instrument [Line Items]
Long-term debt	$ 277		$ 279