Income taxes - Components of deferred income tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets:
Stock compensation	$ 220	$ 244
Accrued expenses	219	215
Deferred loss and tax credit carryforwards	214	226
Inventories and related reserves	145	147
Retirement costs for defined benefit and retiree health care	82	87
Other	81	101
Total deferred income tax assets, before valuation allowance	961	1,020
Valuation allowance	(128)	(186)
Total deferred income tax assets, after valuation allowance	833	834
Deferred income tax liabilities:
Acquisition-related intangibles and fair-value adjustments	(460)	(565)
International earnings	(32)	(105)
Total deferred income tax liabilities	(492)	(670)
Net deferred income tax asset	$ 341	$ 164