NOTE PAYABLE AND DEBT ISSUANCE COSTS (Details) (USD $)				6 Months Ended	1 Months Ended	6 Months Ended	0 Months Ended	6 Months Ended
	Jun. 30, 2013 Tranche	Dec. 31, 2012		Jun. 30, 2013 Loan Agreement with HC Royalty [Member] Tranche Quarter	Dec. 31, 2012 Loan Agreement with HC Royalty [Member] First Tranche [Member]	Jun. 30, 2013 Loan Agreement with HC Royalty [Member] First Tranche [Member]	May 21, 2013 Loan Agreement with HC Royalty [Member] Second Tranche [Member]	Jun. 30, 2013 Loan Agreement with HC Royalty [Member] Second Tranche [Member]
Debt Instrument [Line Items]
Total amount of loan	$ 50,000,000			$ 50,000,000
Number of tranches in loan	2			2
Amount of loan per tranche	25,000,000			25,000,000
Draw down on loan					25,000,000		25,000,000
Annual fixed interest rate (in hundredths)	10.75%			10.75%
Royalty rate of first threshold of PROCYSBI and future approved product net revenues for calendar year (in hundredths)						6.25%		6.00%
Amount of first threshold of PROCYSBI and future approved product net revenues for calendar year						25,000,000		25,000,000
Royalty rate of amount between first and second threshold of PROCYSBI and future approved product net revenues for calendar year (in hundredths)						3.00%		3.00%
Amount of second threshold of PROCYSBI and future approved product net revenues for calendar year						50,000,000		50,000,000
Royalty rate for amount in excess of second threshold of PROCYSBI and future approved product net revenues for calendar year (in hundredths)						1.00%		1.00%
Accrued royalties				2,000
Note payable outstanding	50,000,000	25,000,000	[1]	50,000,000
Total payment required to terminate loan obligation immediately				97,500,000
Number of fiscal quarters of net revenues included in total loan payment consideration				4
Threshold net revenues during specified period included in total loan payment consideration				100,000,000
Total payment required upon net revenues exceeding threshold during specified period to terminate loan obligation immediately				$ 90,000,000

[1] Derived from the Company's audited consolidated financial statements as of December 31, 2012.