Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended			0 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended					3 Months Ended					3 Months Ended	0 Months Ended	3 Months Ended	1 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended			3 Months Ended
	Feb. 28, 2014 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	May 31, 2006 USD ($)	Dec. 09, 2013 Fusilev [Member] defendant	Jun. 19, 2014 FOLOTYN ANDA [Member] ANDA defendant	Mar. 31, 2015 FOLOTYN [Member]	Mar. 31, 2015 ZEVALIN [Member] USD ($)	Apr. 30, 2012 ZEVALIN [Member] Licensing Agreements [Member] EUR (€)	Mar. 31, 2015 ZEVALIN [Member] Licensing Agreements [Member] Country	Mar. 31, 2015 Talon Therapeutics, Inc. [Member] USD ($)	Dec. 31, 2014 Talon Therapeutics, Inc. [Member] USD ($)	Jul. 17, 2013 Talon Therapeutics, Inc. [Member] USD ($)	Mar. 31, 2015 SPI-2012 [Member] USD ($)	Mar. 31, 2015 Poziotinib [Member] Licensing Agreements [Member] USD ($)	Mar. 31, 2015 Minimum [Member]	Mar. 31, 2015 Minimum [Member] FOLOTYN [Member] USD ($)	Mar. 31, 2015 Maximum [Member] USD ($)	Dec. 31, 2014 Maximum [Member] USD ($)	Mar. 31, 2015 Maximum [Member] FOLOTYN [Member] USD ($)	Jun. 27, 2014 INDIA ZEVALIN [Member] Licensing Agreements [Member] USD ($)	Mar. 31, 2015 INDIA ZEVALIN [Member] Licensing Agreements [Member] USD ($)	Oct. 31, 2008 Allergan [Member] USD ($)	Oct. 31, 2008 Allergan [Member] Common Class A	Nov. 30, 2009 Nippon Kayaku [Member] USD ($)	Mar. 31, 2015 Nippon Kayaku [Member] USD ($)	Feb. 28, 2010 TopoTarget [Member] USD ($)	Mar. 31, 2015 TopoTarget [Member] USD ($)	Jul. 31, 2014 TopoTarget [Member] USD ($)	Feb. 28, 2014 TopoTarget [Member] USD ($)	Mar. 31, 2015 Principal executive office [Member] Nevada [Member]	Mar. 31, 2015 Research and development facility [Member] California [Member]
Long-term Purchase Commitment [Line Items]
Facility lease, non-cancelable operating lease expiring date																															May 31, 2019	May 31, 2019
Milestone payments								$ 5,000,000
Potential milestone achievement		100,000												238,000,000														278,000,000
Minimum number of countries outside U.S. approved ZEVALIN for treatment										40
Fees paid to Bayer for acquiring licensing rights									19,000,000
License Agreement Contractual Terms									15 years												15 years
Up-front non-refundable payment																					500,000		41,500,000
Common stock issued (shares)																								25,000
License fee																							300,000
Licenses Revenue																						3,000,000
Percentage Of Royalty																						20.00%
Amount receivable on approval of oral form of FUSILEV				200,000
Percentage of royalty on annual worldwide sales under condition one							8.00%									20.00%
Percentage of royalty on annual worldwide sales under condition two							9.00%
Percentage of royalty on annual worldwide sales under condition three							11.00%
Amount of annual worldwide sales on which royalty is payable under condition one																				150,000,000
Amount of annual worldwide sales on which royalty is payable under condition two																	150,000,000			300,000,000
Amount of annual worldwide sales on which royalty is payable under condition three																	300,000,000
Additional license fees		66,000,000
Acquisition-related contingent obligations, less current portion		2,751,000	2,441,000								2,700,000	2,400,000						5,100,000	4,900,000
Percentage of royalties on net sale of licensed products																20.00%
Contingent value rights future cash payments											195,000,000		195,000,000
Upfront fee																									15,000,000
Payment related to agreement																										10,000,000
Payment on achievement of commercialization milestones																										126,000,000
Upfront fee																											30,000,000
Percentage of development cost																												70.00%
Percentage of development cost that is funded by TopoTarget for joint development plan																												30.00%
Consideration paid for the rights granted (shares)	1,000,000
Additional payments based on the achievement of certain development																														10,000,000
Aggregate payout value																												17,800,000
Second milestone payment																													25,000,000
Milestone net sales achievement															358,000,000
Deferrals and contributions		$ 5,600,000	$ 4,700,000
Number of additional plaintiffs					3
Number of defendants						5
Number of Abbreviated New Drug Applications						4