Intangible Assets and Goodwill (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Intangible Assets and Goodwill
Goodwill	$ 8,965	$ 8,965
Finite-lived intangible asset
Accumulated Amortization	(5,029)	(4,776)
Total Intangible Assets
Cost of total intangible assets	27,596	27,596
Intangible Assets, Net (Excluding Goodwill)	22,567	22,820
Amgen Amendment
Finite-lived intangible asset
Estimated Life	16 years
Cost	14,500	14,500
Accumulated Amortization	(4,036)	(3,812)
Net	10,464	10,688
Core Technology
Finite-lived intangible asset
Estimated Life	11 years
Cost	1,296	1,296
Accumulated Amortization	(993)	(964)
Net	303	332
IPR&D
Indefinite-lived intangible assets:
Indefinite-lived intangible assets	$ 11,800	$ 11,800