Supplemental financial information - Other income (expense), net (OI&E) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Financial Information [Abstract]
Other income (a)	[1]	$ 150	$ 163	$ 219
Other expense (b)	[2]	(52)	(88)	(64)
Total		$ 98	$ 75	$ 155

[1] Other income includes interest, royalty and lease income; investment gains and losses; and other miscellaneous items. As of January 1, 2017, royalties are recorded in OI&E instead of revenue.

[2] Other expense includes a portion of pension and other retiree benefit costs. It also includes currency gains and losses and tax interest expense.