Collaboration Agreements (EYLEA) (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Aug. 31, 2007	Oct. 31, 2006	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaboration Agreements [Line Items]
Accounts receivable from Bayer			$ 242,014	$ 175,263
Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Percentage of repayment of development balance out of profits				50.00%
Contingent reimbursement obligation			251,000
Revenue Recognition, Milestone Method, Revenue Recognized			0	$ 0	$ 15,000
Levels of twelve months sales at which sales milestone payments were received - 200 million					200,000
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned			$ 13,325	$ 9,010	8,887
Minimum advance notice required to terminate collaboration agreement			6 months
Proceeds from Collaborators	$ 20,000	$ 75,000
Other Research and Development Expense					$ 13,700
Deferred Revenue, Additions	$ 20,000	$ 75,000
maximum advance notice required to terminate collaboration agreement			12 months
starting at sales achievement - $200 million
Collaboration Agreements [Line Items]
Period for Achieving Sales Target for Milestone Payment, Rolling Basis					12 months
sales achievement - 100 million
Collaboration Agreements [Line Items]
Maximum amount of sales milestone payments if total sales achieve specific levels					$ 15,000
Minimum | Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Revenue based on percentage of annual sales in Japan			33.50%
Maximum | Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Revenue based on percentage of annual sales in Japan			40.00%