Fair value of financial instruments and marketable securities - Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	$ 206,018	$ 58,088
Deferred consideration payable	18,900	18,300
Contingent consideration payable	330,900	310,240
Recurring basis \| Total
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	206,018	58,088
Stock appreciation rights liability	1,034	3,814
Deferred consideration payable	38,200	37,700
Contingent consideration payable	270,800	257,040
Contingent consideration payable- net sales milestones and royalties	60,100	53,200
Recurring basis \| Quoted prices in active markets for identical assets (level 1)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	0	0
Stock appreciation rights liability	0	0
Deferred consideration payable	0	0
Contingent consideration payable	0	0
Contingent consideration payable- net sales milestones and royalties	0	0
Recurring basis \| Significant other observable inputs (level 2)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	206,018	58,088
Stock appreciation rights liability	0	0
Deferred consideration payable	38,200	37,700
Contingent consideration payable	0	0
Contingent consideration payable- net sales milestones and royalties	0	0
Recurring basis \| Significant unobservable inputs (level 3)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	0	0
Stock appreciation rights liability	1,034	3,814
Deferred consideration payable	0	0
Contingent consideration payable	270,800	257,040
Agilis \| Significant unobservable inputs (level 3)
Financial assets and liabilities measured at fair value on recurring basis
Contingent consideration payable- net sales milestones and royalties	$ 60,100	$ 53,200

Business Combination, Consideration, Liability, Deferred Consideration Payable

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- Definition

Represents the amount of outstanding stock appreciation rights liability.

+ References

No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
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+ References

No definition available.

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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