Summary of significant accounting policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of business segment | segment	1
Change in estimate of sales deductions for prior period sales as a pct of total sales deductions (less than)	1.00%
Sales return provisions as a percentage of gross product sales (less than)	1.00%
Advertising cost	$ 789	$ 674	$ 620
Present value of lease liabilities	528
Operating lease, Right-of-use asset	$ 469
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Present value of lease liabilities				$ 510
Operating lease, Right-of-use asset				$ 439
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue payment term	30 days
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue payment term	120 days