Debt - Long-Term Debt Obligations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total face value of long-term debt	$ 33,174,000,000		$ 24,820,000,000
Less current portion of long-term debt	(1,155,000,000)		(1,305,000,000)
Long-term debt	31,816,000,000		23,414,000,000
Senior Notes
Debt Instrument [Line Items]
Issuance amount		$ 10,000,000,000.0
Total face value of long-term debt	32,200,000,000
Unamortized discount and issuance costs, net	$ (203,000,000)		(101,000,000)
Weighted average remaining lives term	15 years 9 months 18 days
Senior Notes | 2012 Notes issuance of $3.0 billion
Debt Instrument [Line Items]
Issuance amount	$ 3,000,000,000.0
Stated Interest Rates	2.50%
Effective Interest Rates	2.66%
Total face value of long-term debt	$ 1,250,000,000		1,250,000,000
Weighted average remaining lives term	1 year 10 months 24 days
Senior Notes | 2014 Notes issuance of $6.0 billion
Debt Instrument [Line Items]
Issuance amount	$ 6,000,000,000.0
Total face value of long-term debt	$ 5,000,000,000		5,000,000,000
Weighted average remaining lives term	11 years 9 months 18 days
Senior Notes | 2014 Notes issuance of $6.0 billion | Minimum
Debt Instrument [Line Items]
Stated Interest Rates	3.30%
Effective Interest Rates	3.43%
Senior Notes | 2014 Notes issuance of $6.0 billion | Maximum
Debt Instrument [Line Items]
Stated Interest Rates	4.95%
Effective Interest Rates	5.11%
Senior Notes | 2017 Notes issuance of $17.0 billion
Debt Instrument [Line Items]
Issuance amount	$ 17,000,000,000.0
Total face value of long-term debt	$ 16,000,000,000		17,000,000,000
Weighted average remaining lives term	16 years 2 months 12 days
Senior Notes | 2017 Notes issuance of $17.0 billion | Minimum
Debt Instrument [Line Items]
Stated Interest Rates	2.40%
Effective Interest Rates	2.56%
Senior Notes | 2017 Notes issuance of $17.0 billion | Maximum
Debt Instrument [Line Items]
Stated Interest Rates	5.20%
Effective Interest Rates	4.33%
Senior Notes | 2020 Notes issuance of $10.0 billion
Debt Instrument [Line Items]
Issuance amount	$ 10,000,000,000.0
Total face value of long-term debt	$ 10,000,000,000		0
Weighted average remaining lives term	18 years 8 months 12 days
Senior Notes | 2020 Notes issuance of $10.0 billion | Minimum
Debt Instrument [Line Items]
Stated Interest Rates	0.40%
Effective Interest Rates	0.56%
Senior Notes | 2020 Notes issuance of $10.0 billion | Maximum
Debt Instrument [Line Items]
Stated Interest Rates	2.70%
Effective Interest Rates	2.77%
Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Total face value of long-term debt	$ 338,000,000		740,000,000
Other long-term debt
Debt Instrument [Line Items]
Total face value of long-term debt	$ 586,000,000		$ 830,000,000