Unaudited Quarterly Results (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended															12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 610,412	$ 597,027	[1]	$ 457,642	[1]	$ 439,664	[1]	$ 414,602	[2]	$ 427,687	[2]	$ 304,399	[2]	$ 231,789	[2]	$ 2,104,745	$ 1,378,477	$ 445,824
Net income (loss)	96,806	141,306		87,376		98,874		470,407	[3]	191,468	[3]	76,743	[3]	11,651	[3]	424,362	750,269	(221,760)
Net income (loss) per share - basic	$ 0.98	$ 1.44		$ 0.89		$ 1.02		$ 4.92		$ 2.02		$ 0.81		$ 0.12		$ 4.33	$ 7.92	$ (2.45)
Net income (loss) per share - diluted	$ 0.86	$ 1.25		$ 0.79		$ 0.90		$ 4.08		$ 1.72		$ 0.70		$ 0.11		$ 3.81	$ 6.75	$ (2.45)
Effect of Fourth Quarter Events [Line Items]
Substantive milestone payment	25,000	45,000						10,000		65,000
Income tax benefit								(335,800)								288,998	(335,848)	(1,132)
Antibody Collaboration
Effect of Fourth Quarter Events [Line Items]
Number of families of novel antibodies																2
Up-front payments made to acquire full rights to antibodies																(20,000)	0	0
Ang2
Effect of Fourth Quarter Events [Line Items]
Up-front payments made to acquire full rights to antibodies				10,000
PDGFR-beta
Effect of Fourth Quarter Events [Line Items]
Up-front payments made to acquire full rights to antibodies				$ 10,000

[1] Revenues in the second quarter of 2013 were reduced by two $10 million up-front payments made to Sanofi to acquire full rights to antibodies to PDGF and antibodies to Ang2 in ophthalmology, as described in Note 4 above. Revenues in the third and fourth quarter of 2013 included recognition of sales and substantive development milestones of $45.0 million and $25.0 million, respectively.

[2] Revenues in the third and fourth quarter of 2012 included substantive development milestones of $65.0 million and $10.0 million, respectively.

[3] Net income for the quarter ended December 31, 2012 included an income tax benefit of $335.8 million, primarily attributable to the release of substantially all of the Company's valuation allowance against its deferred tax assets.