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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- Definition

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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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, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Revenue Disclosure [Line Items]
Net product sales	$ 362,378	$ 318,740
Activity of Sales Related Deductions [Roll Forward]
Balance	25,365		24,601
Provision related to current period sales	24,192
Credits/payments	(23,428)
Rebates and Chargebacks
Activity of Sales Related Deductions [Roll Forward]
Balance	4,622		4,400
Provision related to current period sales	6,886
Credits/payments	(6,664)
Distribution Related Fees
Activity of Sales Related Deductions [Roll Forward]
Balance	20,211		19,663
Provision related to current period sales	16,858
Credits/payments	(16,310)
Other Sales Related Deductions
Activity of Sales Related Deductions [Roll Forward]
Balance	532		538
Provision related to current period sales	448
Credits/payments	(454)
Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	79.00%	77.00%
EYLEA
Revenue Disclosure [Line Items]
Net product sales	359,000	313,900
ARCALYST
Revenue Disclosure [Line Items]
Net product sales	$ 3,400	$ 4,800