Collaboration and Financing Agreements (Details) (USD $)	6 Months Ended		6 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended			6 Months Ended			6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Common stock warrant liability [Member]	Dec. 31, 2011 Common stock warrant liability [Member]	Jun. 30, 2012 Embedded derivative liabilities [Member]	Dec. 31, 2011 Embedded derivative liabilities [Member]	Jun. 30, 2012 Mallinckrodt LLC Co-Promotion Agreement [Member]	Jun. 30, 2011 Mallinckrodt LLC Co-Promotion Agreement [Member]	Jun. 30, 2012 Mallinckrodt LLC Co-Promotion Agreement [Member]	Jun. 30, 2011 Mallinckrodt LLC Co-Promotion Agreement [Member]	Jun. 06, 2012 Mallinckrodt LLC Co-Promotion Agreement [Member]	Jun. 30, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Mar. 31, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jun. 30, 2011 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jun. 30, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jun. 30, 2011 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Dec. 20, 2011 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jun. 30, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member] Minimum [Member]	Jun. 30, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member] Maximum [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Common stock warrant liability [Member]	Jun. 30, 2011 Healthcare Royalty Financing Agreement [Member] Common stock warrant liability [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Common stock warrant liability [Member]	Jun. 30, 2011 Healthcare Royalty Financing Agreement [Member] Common stock warrant liability [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Embedded derivative liabilities [Member]	Jun. 30, 2011 Healthcare Royalty Financing Agreement [Member] Embedded derivative liabilities [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Embedded derivative liabilities [Member]	Jun. 30, 2011 Healthcare Royalty Financing Agreement [Member] Embedded derivative liabilities [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Mar. 31, 2012 Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Scenario 2 [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Scenario 3 [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Minimum [Member] Scenario 1 [Member]	Jun. 30, 2012 Healthcare Royalty Financing Agreement [Member] Maximum [Member] Scenario 1 [Member]
Collaboration and Financing Agreements (Textual) [Abstract]
Company entered into the co-promotion agreement with Mallinckrodt											Jun. 06, 2012
Company entered into the co-promotion agreement with Astellas															2009-07
Co-promotion agreement early termination date									Jun. 30, 2014						Mar. 31, 2012					Mar. 31, 2018
Co-promotion agreement termination notice period									60 days
Non-refundable up-front payment															$ 2,000,000
Additional payments on achievement of series of milestones															18,000,000
Percentage of service fee paid																		45.00%	55.00%
Financing agreement termination date									2012-08						2013-06
Initially recorded upfront and milestone payments received from Astellas as deferred revenue															20,000,000
Amortizing the upfront and milestone payments as contract revenue recognized												0		1,563,000	8,462,000	3,126,000
Estimated present value of tail payments																	5,291,000
Tail payment liability												4,490,000			4,490,000
Tail payment liability related interest expense												164,000			321,000
Amortizing the upfront and milestone payments as contract revenue recognized													8,462,000
Recognized shared marketing expense												56,000		864,000	253,000	1,148,000
Incurred service fee expenses							0	0	0	0		58,000		1,675,000	1,757,000	3,184,000
Company closed royalty financing agreement																					Jul. 18, 2011
Borrowed amount from Healthcare Royalty																				30,000,000
Common stock issued and sold to Healthcare Royalty, amount	66,000	65,000																		1,500,000
Common stock issued and sold to Healthcare Royalty, shares	32,500,000																			388,601
Common stock issued and sold to Healthcare Royalty, price per share																				$ 3.86
Warrant exercisable to Healthcare Royalty, shares	225,000
Warrant exercisable to Healthcare Royalty, price per share																				$ 9.00
Term of warrant exercisable																				10 years
Revenue Interest																				0.50%											5.00%	2.50%	5.00%	5.00%	5.75%
Net product sales amount received																				10,000,000										75,000,000		75,000,000	150,000,000
Borrowed internal rate of return																														19.00%		17.00%
Fair value of embedded derivatives			387,000	345,000	477,000	845,000																				477,000		477,000
Aggregate net proceed from financing agreement																				29,485,000
Amortized discount																				476,000				790,000				605,000
Three fixed payments																				January 31, 2015, January 31, 2016 and January 31, 2017
Prepayment requires consent of lenders	25,000,000
Terminate payment base amount																				75,000,000										52,500,000		45,000,000
Change in fair value			$ 42,000		$ (368,000)																	$ (91,000)	$ (91,000)	$ (42,000)	$ (42,000)	$ 330,000	$ 330,000	$ 368,000	$ 368,000