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Debt and lines of credit - Additional Information (Details) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended
Feb. 28, 2021
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Debt Instrument [Line Items]          
Commercial paper   $ 0   $ 0  
Retirement of debt       550,000,000 $ 500,000,000
Interest and debt expense   44,000,000 $ 48,000,000 90,000,000 $ 93,000,000
Notes due 2021 at 2.75%          
Debt Instrument [Line Items]          
Retirement of debt $ 550,000,000        
Revolving credit facility          
Debt Instrument [Line Items]          
Line of credit facility, maximum borrowing capacity   $ 2,000,000,000   $ 2,000,000,000