INTANGIBLE ASSETS - Additional Information (Details) - USD ($) $ in Thousands			9 Months Ended	12 Months Ended
	Mar. 31, 2015	Mar. 26, 2014	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 29, 2014
Finite-Lived Intangible Assets [Line Items]
Net Book Value				$ 161,536	$ 94,265
Impairment of intangible assets				4,710	0	$ 0
Finite-lived intangible asset				$ 179,096	99,867
Remaining weighed average period of amortization (in years)				11 years 22 days
Cash paid upon consummation				$ 33,430	29,150	0
Other Expense
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets			$ 4,700
Minimum
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)				1 year
Maximum
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)				16 years
Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Cash paid upon consummation		$ 29,150
Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Discount rate percentage				19.00%
Cash paid upon consummation	$ 33,430
Common stock shares issued (in shares)	661,279
Value of common stock	$ 15,844
Ligand License Agreement
Finite-Lived Intangible Assets [Line Items]
Net Book Value						2,500
Require To Make Substantial Payments Payable Upon Achievement Of Milestones						$ 105,500
Payment of amendment consideration				$ 1,000
Finite-lived intangible asset				3,300
Ligand License Agreement | Minimum
Finite-Lived Intangible Assets [Line Items]
Annual Royalty Percentage						15.00%
Ligand License Agreement | Maximum
Finite-Lived Intangible Assets [Line Items]
Annual Royalty Percentage						17.00%
Chenodal Product Rights
Finite-Lived Intangible Assets [Line Items]
Net Book Value				60,360
Finite-lived intangible asset				$ 67,849
Assets useful life (in years)				16 years
Product rights
Finite-Lived Intangible Assets [Line Items]
Net Book Value					67,952
Finite-lived intangible asset					$ 71,372
Assets useful life (in years)					16 years
Product rights | Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives		$ 71,372
Assets useful life (in years)		16 years		16 years
Product rights | Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)	10 years
Trade Name
Finite-Lived Intangible Assets [Line Items]
Net Book Value				$ 0	$ 41
Finite-lived intangible asset				$ 175	$ 175
Assets useful life (in years)				1 year	1 year
Trade Name | Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives		$ 175		$ 200
Assets useful life (in years)		1 year		1 year
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Net Book Value				$ 332	$ 372
Finite-lived intangible asset				$ 403	$ 403
Assets useful life (in years)				10 years	10 years
Customer relationships | Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives		$ 403		$ 400
Assets useful life (in years)		10 years		10 years
Vecamyl
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset				$ 3,600
Thiola License Agreement
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)					10 years
Remaining weighed average period of amortization (in years)					8 years 4 months 24 days
Thiola License Agreement | Mission Pharmacal Company
Finite-Lived Intangible Assets [Line Items]
Present value of guaranteed minimum royalties payable				$ 10,900
Discount rate percentage				11.00%
Mission an up-front license fee							$ 3,000
Guaranteed minimum royalties							$ 2,000
Thiola License Agreement | Mission Pharmacal Company | Other Current Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties				$ 800
Thiola License Agreement | Mission Pharmacal Company | Other Noncurrent Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties				10,100
Thiola Asset
Finite-Lived Intangible Assets [Line Items]
Net Book Value				21,340	$ 14,179
Finite-lived intangible asset				$ 24,133	$ 15,049
Assets useful life (in years)				10 years	10 years
United States | Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest	$ 75,900
International | Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest	7,300
Purchase Agreement | Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Value of common stock	$ 9,000