Summary of significant accounting policies - Narrative 2 (Details) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) item category	Jun. 30, 2016 USD ($)
Revenue Recognition
Percentage of Medicare Part D insurance coverage gap mandate to be funded by manufacturers				50.00%
Categories of milestone events, number | category				3
Number of stages of life-cycle drugs | item				3
Stock-Based Compensation
Stock-based compensation expense		$ 33,800	$ 21,300	$ 64,400	$ 42,100
Recent Accounting Pronouncements
Provision (benefit) for income taxes		$ 3,100	$ 785	$ (7,800)	$ 1,185
Accounting Standards Update 2016-16
Recent Accounting Pronouncements
Deferred tax assets	$ 34,900
Reversal of long-term prepaid taxes	(2,100)
Provision (benefit) for income taxes	$ 2,100
ICLUSIG
Revenue Recognition
Amortization period				12 years 6 months