Collaboration and Financing Agreements - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended			0 Months Ended	1 Months Ended			0 Months Ended			3 Months Ended			3 Months Ended				3 Months Ended			3 Months Ended		3 Months Ended		3 Months Ended	12 Months Ended		12 Months Ended		0 Months Ended	3 Months Ended	1 Months Ended		3 Months Ended				1 Months Ended
	Jul. 18, 2011	Jul. 18, 2011	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Jul. 30, 2012 Oxford/SVB [Member]	Jun. 30, 2012 Oxford/SVB [Member]	Mar. 31, 2013 Oxford/SVB [Member]	Jun. 30, 2011 Oxford/SVB [Member]	Jul. 30, 2012 Oxford/SVB [Member] Revolving Credit Facility [Member]	Jun. 30, 2011 Oxford/SVB [Member] Revolving Credit Facility [Member]	Jun. 30, 2008 Loan And Security Agreement [Member]	Mar. 31, 2013 Embedded Derivative Liabilities [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member] Embedded Derivative Liabilities [Member]	Mar. 31, 2012 Healthcare Royalty Financing Agreement [Member] Embedded Derivative Liabilities [Member]	Dec. 31, 2012 Healthcare Royalty Financing Agreement [Member] Embedded Derivative Liabilities [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member] Embedded Derivative Liabilities [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member] Common Stock Warrant Liabilities [Member]	Mar. 31, 2012 Healthcare Royalty Financing Agreement [Member] Common Stock Warrant Liabilities [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member] Common Stock Warrant Liabilities [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member] Scenario 2 [Member]	Jul. 18, 2011 Healthcare Royalty Financing Agreement [Member] Scenario 2 [Member]	Mar. 31, 2013 Healthcare Royalty Financing Agreement [Member] Scenario 3 [Member]	Dec. 31, 2012 Minimum [Member] Oxford/SVB [Member]	Jul. 18, 2011 Minimum [Member] Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Dec. 31, 2012 Maximum [Member] Oxford/SVB [Member]	Jul. 18, 2011 Maximum [Member] Healthcare Royalty Financing Agreement [Member] Scenario 1 [Member]	Jun. 06, 2012 Mallinckrodt LLC Co-Promotion Agreement [Member]	Mar. 31, 2013 Mallinckrodt LLC Co-Promotion Agreement [Member]	Aug. 31, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jul. 31, 2009 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Mar. 31, 2013 Astellas Pharma Us Inc Co Promotion Agreement [Member] tail_payments	Mar. 31, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Dec. 31, 2012 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Dec. 20, 2011 Astellas Pharma Us Inc Co Promotion Agreement [Member]	Jul. 31, 2009 Astellas Pharma Us Inc Co Promotion Agreement [Member] Minimum [Member]	Jul. 31, 2009 Astellas Pharma Us Inc Co Promotion Agreement [Member] Maximum [Member]
Debt Instrument [Line Items]
Company Entered Into Co Promotion Agreement																																				2009-07
Line of Credit Facility, Interest Rate During Period																												3.29%		7.29%
Co-Promotion Agreement, Renewal Period																																6 months
Sales Period For Tail Payment																																12 months
Co-promotion agreement termination notice period																																	60 days
Incurred Service Fee Expenses																																	$ 143,000			$ 0	$ 1,699,000
Non-refundable up-front payment																																			2,000,000
Milestone Payments																																			18,000,000
Service Fee Rate																																								45.00%	55.00%
Deferred Agreement Payments																																			20,000,000
Deferred contract revenues																																					8,462,000
Number Of Annual Tail Payments																																				2
Tail payment liability related interest expense																																				141,000	157,000
Service fee reduction																																		1,500,000
Tail payment liability																																				2,936,000	2,795,000		5,291,000
Reduction to tail payment liability																																		742,000
Present value of the service fee receivable and tail payment																																						1,924,000
Recognized shared marketing expense																																				0	255,000
Debt instrument, outstanding												18,000,000			30,000,000
Common stock issued and sold to Healthcare Royalty, amount			101,000		101,000										1,500,000
Common stock issued and sold to Healthcare Royalty, shares														388,601
Common stock issued and sold to Healthcare Royalty, price per share														$ 3.86
Warrant exercisable to Healthcare Royalty, shares	225,000	225,000
Warrant exercisable to Healthcare Royalty, price per share (usd per share)	$ 9.00													$ 9.00
Term of warrant exercisable														10 years
Revenue Interest Rate														0.50%										5.00%		2.50%	0.50%		5.00%		5.75%
Net product sales amount received														10,000,000									75,000,000		75,000,000		150,000,000
Fixed Debt Repayment Dates														January 31, 2015, January 31, 2016 and January 31, 2017
Fixed Payments for Jan 31,2015														10,000,000
Fixed Payments for Jan 31,2016														10,000,000
Fixed Payments for Jan 31,2017														10,000,000
Agreement Expiration Date																																	2014-06-30			2012-03-31
Agreement termination date														Mar. 31, 2018
Intercreditor loan			25,000,000						25,000,000		10,000,000
Terminate payment base amount														75,000,000									52,500,000		45,000,000
Borrowed internal rate of return																							19.00%		17.00%
Fair value of embedded derivatives																1,073,000		992,000
Aggregate net proceed from financing agreement														29,485,000
Financing discounts															476,000				605,000			790,000
Change in fair value													81,000			(81,000)	38,000			(76,000)	49,000
Revolving credit facility									10,000,000
Term loan, interest rate							12.06%
Revolving credit facility, interest rate							equal to the greater of 3.29% above SVB’s prime rate or 7.29%
Percentage paid for unused portion of revolving credit facility							0.50%
Principal and interest repaid			0	7,013,000		19,492,000
Final Payment to Terminate Debt						1,200,000
Prepayment Premium to Terminate Debt						$ 400,000				$ 100,000
Percentage of principal as per payment premium								2.00%
Financing Agreement Termination Date																																				2013-06