Supplemental financial information - Other long-term liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Text Block Supplement [Abstract]
Long-term portion of transition tax on indefinitely reinvested earnings	$ 457	$ 506
Deferred compensation plans	350	298
Operating lease liabilities	249	259
Uncertain tax positions	89	303
Other	160	148
Total	$ 1,305	$ 1,514