Income taxes (Details 5) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating loss and Tax credit carryforwards
Valuation allowance for deferred tax assets	$ 1,102	$ 816
U.S foreign tax credit carryforwards	920
U.S. state taxing jurisdictions | 2017-2036
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	1,425
Valuation allowance for deferred tax assets	442
U.S. state taxing jurisdictions | Expiration date next one to fifteen years
Operating loss and Tax credit carryforwards
Tax credit carryforwards	$ 137
State tax credit carryforward expiration date, minimum	5 years
State tax credit carryforwards expiration date, maximum	15 years
Non-U.S. taxing jurisdictions
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	$ 4,055
Valuation allowance for deferred tax assets	660
Non-U.S. taxing jurisdictions | Expiring in 2017
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	3
Non-U.S. taxing jurisdictions | Expiring in 2018
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	64
Non-U.S. taxing jurisdictions | Expiring in 2019
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	159
Non-U.S. taxing jurisdictions | Expire between 2020-2022
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	470
Non-U.S. taxing jurisdictions | Expire between 2023-2037
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	168
Non-U.S. taxing jurisdictions | Unlimited
Operating loss and Tax credit carryforwards
Net operating loss carryforwards	$ 3,191