Income taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Deferred loss and tax credit carryforwards	$ 247	$ 256
Accrued expenses	129	119
Stock compensation	122	107
Inventories and related reserves	107	93
Retirement costs for defined benefit and retiree health care	80	38
Other	0	9
Total deferred tax assets, before valuation allowance	685	622
Valuation allowance	(172)	(165)
Total deferred tax assets, after valuation allowance	513	457
Deferred tax liabilities:
Acquisition-related intangibles and fair-value adjustments	(142)	(207)
International earnings	(43)	(64)
Other	(75)	0
Total deferred tax liabilities	(260)	(271)
Net deferred tax asset	$ 253	$ 186