Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013
Purchase Commitments
Remaining purchase commitments under various agreements with third-parties	$ 6,800,000
Other Funding Commitments
Accrued expenses for clinical studies	300,000
Minimum
Indemnification Obligations
Estimated term to defend the validity of patent through the appeals process	2 years
Ferumoxytol term of data and market exclusivity even if there is no successful outcome from the appeals process	8 years
Maximum
Indemnification Obligations
Initial indemnification exposure for actions or events involving officers, directors and certain employees	1,000,000
Estimated term to defend the validity of patent through the appeals process	3 years
Ferumoxytol term of data and market exclusivity even if there is no successful outcome from the appeals process	10 years
Real property
Facility Lease Obligations
Expenses associated with operating leases	1,500,000	1,700,000	1,700,000
Initial lease term	5 years 2 months
Number of successive five year extension terms	1
Extension period of the lease terms	5 years
Minimum Lease Payments
Year Ended December 31, 2014	1,128,000
Year Ended December 31, 2015	1,128,000
Year Ended December 31, 2016	1,128,000
Year Ended December 31, 2017	1,128,000
Thereafter	1,034,000
Total	5,546,000
Security deposit in the form of an irrevocable letter of credit				400,000
Security deposit as of second anniversary of the commencement date				300,000
Office equipment
Facility Lease Obligations
Expenses associated with operating leases	(300,000)	900,000	800,000
Minimum Lease Payments
Year Ended December 31, 2014	$ 100,000