Debt - Long Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2020	Oct. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total debt	$ 13,299			$ 13,812
Less: unamortized discounts and issuance costs	(1,130)			(1,158)
Total debt, net	12,169			12,654
Less: current portion	(500)			(1,250)
Long-term debt, net	$ 11,669			11,404
2.50% due 2020
Debt Instrument [Line Items]
Interest rate	2.50%	250.00%	2.50%
Total debt	$ 0			1,250
3.35% due 2021
Debt Instrument [Line Items]
Interest rate	3.35%		3.35%
Total debt	$ 500			900
3.10% due 2023
Debt Instrument [Line Items]
Interest rate	3.10%
Total debt	$ 500			500
2.90% due 2025
Debt Instrument [Line Items]
Interest rate	2.90%
Total debt	$ 750			750
3.55% due 2026
Debt Instrument [Line Items]
Interest rate	3.55%
Total debt	$ 2,000			2,000
1.85% due 2030
Debt Instrument [Line Items]
Interest rate	1.85%
Total debt	$ 400			0
3.60% due 2035
Debt Instrument [Line Items]
Interest rate	3.60%
Total debt	$ 500			500
4.50% and 6.15% due 2036
Debt Instrument [Line Items]
Total debt	$ 1,054			1,054
4.50% and 6.15% due 2036 | Minimum
Debt Instrument [Line Items]
Interest rate	4.50%
4.50% and 6.15% due 2036 | Maximum
Debt Instrument [Line Items]
Interest rate	615.00%
4.07% due 2042
Debt Instrument [Line Items]
Interest rate	4.07%
Total debt	$ 1,336			1,336
3.80% due 2045
Debt Instrument [Line Items]
Interest rate	3.80%
Total debt	$ 1,000			1,000
4.70% due 2046
Debt Instrument [Line Items]
Interest rate	4.70%
Total debt	$ 1,326			1,326
2.80% due 2050
Debt Instrument [Line Items]
Interest rate	2.80%
Total debt	$ 750			0
4.09% due 2052
Debt Instrument [Line Items]
Interest rate	4.09%
Total debt	$ 1,578			1,578
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041
Debt Instrument [Line Items]
Total debt	$ 1,605			$ 1,618
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041 | Minimum
Debt Instrument [Line Items]
Interest rate	4.85%
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041 | Maximum
Debt Instrument [Line Items]
Interest rate	9.13%