INTANGIBLE ASSETS - Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014	Nov. 03, 2017
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (51,046)	$ (33,497)
Intangible assets finite-lived, net	159,317
Intangible assets, gross (excluding goodwill)	235,863	215,540
Intangible Assets, Net (Excluding Goodwill)	$ 184,817	$ 182,043
Chenodal Product Rights
Finite-Lived Intangible Assets [Line Items]
Useful Life	16 years	16 years
Intangible assets acquired with definite lives			$ 67,849
Finite-lived intangible asset, gross	$ 67,849
Accumulated Amortization	(15,976)	$ (11,738)
Intangible assets finite-lived, net	51,873	$ 56,111
Thiola License
Finite-Lived Intangible Assets [Line Items]
Useful Life		10 years
Finite-lived intangible asset, gross	54,471	$ 35,339		$ 5,900
Accumulated Amortization	(10,168)	(5,818)
Intangible assets finite-lived, net	$ 44,303	$ 29,521
Economic Interest - U.S. revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Finite-lived intangible asset, gross	$ 75,900	$ 75,900
Accumulated Amortization	(20,903)	(13,320)
Intangible assets finite-lived, net	$ 54,997	$ 62,580
Economic Interest - Int'l revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Finite-lived intangible asset, gross	$ 8,058	$ 7,074
Accumulated Amortization	(2,219)	(1,241)
Intangible assets finite-lived, net	5,839	5,833
Economic Interest - L-UDCA (acquired IPR&D)
Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	$ 25,500	$ 25,500
Ligand License
Finite-Lived Intangible Assets [Line Items]
Useful Life	11 years	11 years
Finite-lived intangible asset, gross	$ 3,300	$ 3,300
Accumulated Amortization	(1,420)	(1,093)
Intangible assets finite-lived, net	$ 1,880	$ 2,207
Manchester Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Finite-lived intangible asset, gross	$ 403	$ 403
Accumulated Amortization	(152)	(112)
Intangible assets finite-lived, net	$ 251	$ 291
Manchester Trade Name
Finite-Lived Intangible Assets [Line Items]
Useful Life	1 year	1 year
Finite-lived intangible asset, gross	$ 175	$ 175
Accumulated Amortization	(175)	(175)
Intangible assets finite-lived, net	$ 0	$ 0
Internal Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years
Finite-lived intangible asset, gross	$ 207
Accumulated Amortization	(33)
Intangible assets finite-lived, net	$ 174
Manchester Pharmaceuticals LLC | Chenodal Product Rights
Finite-Lived Intangible Assets [Line Items]
Useful Life			16 years
Intangible assets acquired with definite lives			$ 67,800
Manchester Pharmaceuticals LLC | Manchester Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life			10 years
Intangible assets acquired with definite lives			$ 400
Manchester Pharmaceuticals LLC | Manchester Trade Name
Finite-Lived Intangible Assets [Line Items]
Useful Life			1 year
Intangible assets acquired with definite lives			$ 200