Intangible Assets and Goodwill (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Intangible Assets and Goodwill
Goodwill	$ 8,965	$ 8,965
Finite-lived intangible asset
Accumulated Amortization	(4,523)	(3,763)
Total Intangible Assets
Cost of total intangible assets	27,596	27,596
Intangible Assets, Net (Excluding Goodwill)	23,073	23,833
Amgen Amendment
Finite-lived intangible asset
Estimated Life	16 years
Cost	14,500	14,500
Accumulated Amortization	(3,587)	(2,915)
Net	10,913	11,585
Core Technology
Finite-lived intangible asset
Estimated Life	11 years
Cost	1,296	1,296
Accumulated Amortization	(936)	(848)
Net	360	448
IPR&D
Indefinite-lived intangible assets:
Indefinite-lived intangible assets	$ 11,800	$ 11,800