Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Debt and lines of credit - Additional Information (Details) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Commercial paper	$ 0				$ 0
Proceeds from issuance of long-term debt					1,498,000,000	$ 1,491,000,000
Interest and debt expense	$ 49,000,000			$ 43,000,000	$ 142,000,000	$ 125,000,000
Notes due 2020 at 1.75%
Debt Instrument [Line Items]
Retirement of debt		$ 500,000,000
Long-term debt stated interest rate (in percentage)	1.75%				1.75%
Notes due 2025 at 1.375%
Debt Instrument [Line Items]
Principal amount			$ 750,000,000
Payments of debt issuance costs			4,000,000
Proceeds from issuance of long-term debt			$ 749,000,000
Long-term debt stated interest rate (in percentage)	1.375%				1.375%
Notes due 2030 at 1.75%
Debt Instrument [Line Items]
Principal amount		750,000,000
Payments of debt issuance costs		5,000,000
Proceeds from issuance of long-term debt		$ 749,000,000
Long-term debt stated interest rate (in percentage)	1.75%				1.75%
Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,000,000,000				$ 2,000,000,000