Debt - October Exchange Offers (Details)	1 Months Ended
	Oct. 27, 2020 USD ($) transaction Debt_Instrument	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)
Debt Instrument [Line Items]
Principal Amount Issued		$ 2,123,000,000	$ 5,885,000,000
October Exchange Offers | Subsequent Event
Debt Instrument [Line Items]
Number of note series exchanged | Debt_Instrument	17
Number of exchange offer transactions | transaction	2
October Exchange Offer One | Subsequent Event
Debt Instrument [Line Items]
Principal amount exchanged	$ 1,000,000,000.0
October Exchange Offer One | 1.680% Notes Due 2030 | Subsequent Event
Debt Instrument [Line Items]
Principal Amount Issued	$ 1,100,000,000
Stated interest rate on debt instrument	1.68%
October Exchange Offer One | Notes Maturing In 2021 | Subsequent Event
Debt Instrument [Line Items]
Principal amount exchanged	$ 31,000,000
October Exchange Offer Two | Subsequent Event
Debt Instrument [Line Items]
Principal amount exchanged	3,700,000,000
Debt exchange offer, cash	748,000,000
October Exchange Offer Two | 2.987% Notes Due 2056 | Subsequent Event
Debt Instrument [Line Items]
Principal Amount Issued	$ 4,500,000,000
Stated interest rate on debt instrument	2.987%