Contingencies and commitments (U.S. Repatriation Tax Commitments) (Details) $ in Millions	Dec. 31, 2019 USD ($) installment
Commitments and Contingencies Disclosure [Abstract]
U.S. repatriation tax commitments, number of annual installments | installment	8
U.S. repatriation tax commitments, 2020	$ 587
U.S. repatriation tax commitments, 2021	587
U.S. repatriation tax commitments, 2022	587
U.S. repatriation tax commitments, 2023	1,100
U.S. repatriation tax commitments, 2024	1,467
U.S. repatriation tax commitments, Thereafter	1,834
Total remaining U.S. repatriation tax commitments	$ 6,162