For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

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Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to accounts other than costs and expenses.

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Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

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Net Product Sales (Details) - USD ($) $ in Thousands	3 Months Ended
Net Product Sales (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Revenue Disclosure [Line Items]
Net product sales	$ 987,909	$ 858,245
Activity of Sales Related Deductions [Roll Forward]
Balance	109,319	56,033	$ 85,302	$ 45,851
Provision related to current period sales	111,381	89,603
Credits/payments	(87,364)	(79,421)
Rebates and Chargebacks
Activity of Sales Related Deductions [Roll Forward]
Balance	47,661	23,118	29,840	12,712
Provision related to current period sales	48,495	38,908
Credits/payments	(30,674)	(28,502)
Distribution Related Fees
Activity of Sales Related Deductions [Roll Forward]
Balance	43,833	28,353	34,142	29,465
Provision related to current period sales	51,716	41,175
Credits/payments	(42,025)	(42,287)
Other Sales Related Deductions
Activity of Sales Related Deductions [Roll Forward]
Balance	17,825	4,562	$ 21,320	$ 3,674
Provision related to current period sales	11,170	9,520
Credits/payments	$ (14,665)	$ (8,632)
Besse Medical [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	55.00%	53.00%
EYLEA
Revenue Disclosure [Line Items]
Net product sales	$ 984,049	$ 854,387
ARCALYST
Revenue Disclosure [Line Items]
Net product sales	$ 3,860	$ 3,858
McKesson Corporation [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	40.00%	27.00%
Curascript SD [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage		19.00%
Minimum [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	10.00%	10.00%