Balance Sheet Account Detail - Components of Intangible Assets Net of Accumulated Amortization (Detail) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 10, 2016	May 29, 2013	Mar. 31, 2016	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Product Rights [Line Items]
Historical Cost					$ 305,668		$ 305,668
Accumulated Amortization					(115,167)		(102,797)
Foreign Currency Translation					(4,006)		(4,353)
Impairment					(8,183)		(8,183)
Net Amount					178,312		190,335
Ligand Pharmaceuticals Inc [Member]
Product Rights [Line Items]
Milestone payments	$ 6,000		$ 6,000
MARQIBO IPR&D (NHL indication) [Member]
Product Rights [Line Items]
Historical Cost					17,600		17,600
Accumulated Amortization					0		0
Foreign Currency Translation					0		0
Impairment					0		0
Net Amount					17,600		17,600
EVOMELA distribution rights [Member]
Product Rights [Line Items]
Historical Cost					7,700		7,700
Accumulated Amortization					(148)		0
Foreign Currency Translation					0		0
Impairment					0		0
Net Amount					$ 7,552		7,700
Full Amortization Period (months)					156 months
Remaining Amortization Period (months)					153 months
BELEODAQ distribution rights [Member]
Product Rights [Line Items]
Historical Cost					$ 25,000		25,000
Accumulated Amortization					(3,750)		(2,812)
Foreign Currency Translation					0		0
Impairment					0		0
Net Amount					$ 21,250		22,188
Full Amortization Period (months)					160 months
Remaining Amortization Period (months)					136 months
MARQIBO distribution rights [Member]
Product Rights [Line Items]
Historical Cost					$ 26,900		26,900
Accumulated Amortization					(10,703)		(8,544)
Foreign Currency Translation					0		0
Impairment					0		0
Net Amount					$ 16,197		18,356
Full Amortization Period (months)					81 months
Remaining Amortization Period (months)					45 months
FOLOTYN distribution rights [Member]
Product Rights [Line Items]
Historical Cost					$ 118,400		118,400
Accumulated Amortization					(34,498)		(29,474)
Foreign Currency Translation					0		0
Impairment		$ (1,000)			0		0
Net Amount					$ 83,902		88,926
Full Amortization Period (months)					152 months
Remaining Amortization Period (months)					77 months
ZEVALIN distribution rights [Member] | United States [Member]
Product Rights [Line Items]
Historical Cost					$ 41,900		41,900
Accumulated Amortization					(32,346)		(30,608)
Foreign Currency Translation					0		0
Impairment					0		0
Net Amount					$ 9,554		11,292
Full Amortization Period (months)					123 months
Remaining Amortization Period (months)					33 months
ZEVALIN distribution rights [Member] | Ex-U.S. [Member]
Product Rights [Line Items]
Historical Cost					$ 23,490		23,490
Accumulated Amortization					(13,634)		(12,632)
Foreign Currency Translation					(4,006)		(4,353)
Impairment					0		0
Net Amount					$ 5,850		6,505
Full Amortization Period (months)					96 months
Remaining Amortization Period (months)					45 months
FUSILEV distribution rights [Member]
Product Rights [Line Items]
Historical Cost					$ 16,778		16,778
Accumulated Amortization					(9,618)		(9,618)
Foreign Currency Translation					0		0
Impairment					(7,160)		(7,160)
Net Amount					$ 0		0
Full Amortization Period (months)					56 months
Remaining Amortization Period (months)					0 months
FOLOTYN out-License [Member]
Product Rights [Line Items]
Historical Cost					$ 27,900		27,900
Accumulated Amortization					(10,470)		(9,109)
Foreign Currency Translation					0		0
Impairment					(1,023)		(1,023)
Net Amount					$ 16,407		$ 17,768
Full Amortization Period (months)					110 months
Remaining Amortization Period (months)					73 months
FUSILEV [Member]
Product Rights [Line Items]
Impairment				$ (7,200)		$ (7,200)
EVOMELA [Member]
Product Rights [Line Items]
Historical Cost			$ 7,700