Summary of significant accounting policies - Narrative 2 (Details) $ in Thousands		3 Months Ended
	Jan. 01, 2017 USD ($)	Mar. 31, 2017 USD ($) item category	Mar. 31, 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		$ 30,600	$ 20,800
Recent Accounting Pronouncements
Provision (benefit) for income taxes		(10,900)	$ 400
Accounting Standards Update 2016-16
Recent Accounting Pronouncements
Deferred tax assets	$ 34,900	$ 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