Summary of significant accounting policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
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	$ 674	$ 620	$ 489
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (17,977)	(5,072)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit		$ 25
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue payment term	30 days
Minimum [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability				$ 400
Operating lease, Right-of-use asset				400
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue payment term	120 days
Maximum [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability				450
Operating lease, Right-of-use asset				$ 450