Commitments and Contingencies (Details) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2008 item	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Purchase Commitments
Remaining purchase commitments under various agreements with third-parties		$ 3,700,000
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
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
Automobiles, laboratory and office equipment
Operating and Facility Lease Obligations
Expenses associated with operating leases		900,000	800,000	1,000,000
Number of automobiles leased for field-based employees		76
Initial lease term per automobile		12 months
Minimum Lease Payments
Year Ended December 31, 2013		100,000
Real property
Operating and Facility Lease Obligations
Expenses associated with operating leases		1,700,000	1,700,000	1,700,000
Number of successive five year extension terms	2
Extension period of the lease terms	5 years
Amount received as tenant improvement reimbursements from the landlord	2,200,000
Minimum Lease Payments
Year Ended December 31, 2013		2,071,000
Year Ended December 31, 2014		2,127,000
Year Ended December 31, 2015		2,183,000
Year Ended December 31, 2016		1,556,000
Total		7,937,000
Security deposit in the form of an irrevocable letter of credit	$ 500,000