Commitments and Contingencies - Additional Information (Detail) € in Millions							1 Months Ended							3 Months Ended
	Mar. 10, 2016 USD ($)	Jan. 08, 2016 USD ($)	Nov. 16, 2015 USD ($)	Oct. 27, 2015 USD ($)	Jun. 27, 2014 USD ($)	Jun. 19, 2014 defendant ANDA	Mar. 31, 2016 USD ($)	Jan. 31, 2016 USD ($)	Feb. 28, 2014 USD ($)	Apr. 30, 2012 EUR (€)	Feb. 28, 2010 USD ($)	Nov. 30, 2009 USD ($)	Oct. 31, 2008 USD ($) shares	Mar. 31, 2016 USD ($) Country shares	Dec. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Jul. 17, 2013 USD ($)	May. 31, 2006 USD ($)
Long-term Purchase Commitment [Line Items]
Potential milestone achievement							$ 100,000							$ 100,000	$ 100,000
Deferred revenue							2,908,000							2,908,000	6,513,000
Amount receivable on approval of oral form of FUSILEV																			$ 200,000
Additional license fees														66,000,000
Acquisition-related contingent obligations, less current portion							1,708,000							1,708,000	1,439,000
Consideration paid for the rights granted (shares)									$ 1,000,000
Deferrals and contributions							$ 7,100,000							$ 7,100,000	6,500,000
Settlement amount				$ 7,000,000
Legal fees				$ 200,000
FOLOTYN ANDA [Member]
Long-term Purchase Commitment [Line Items]
Number of defendants | defendant						5
Number of Abbreviated New Drug Applications | ANDA						4
FOLOTYN [Member]
Long-term Purchase Commitment [Line Items]
Percentage of royalty on annual worldwide sales under condition one							8.00%							8.00%
Percentage of royalty on annual worldwide sales under condition two							9.00%							9.00%
Percentage of royalty on annual worldwide sales under condition three							11.00%							11.00%
Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Potential payment			$ 2,000,000
ZEVALIN, FOLOTYN, BELEODAQ, And MARQIBO [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received		$ 6,000,000						$ 6,000,000
Total Consideration [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received			18,000,000
Milestone net sales achievement															15,000,000
Payment One [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received			15,000,000
Payment Two [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received			$ 3,000,000
Milestone net sales achievement														$ 400,000
Deferred revenue							$ 2,500,000							2,500,000
Ligand Pharmaceuticals Inc [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments	$ 6,000,000						6,000,000
ZEVALIN [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments														$ 5,000,000
ZEVALIN [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
Minimum number of countries outside U.S. approved ZEVALIN for treatment | Country														40
Fees paid to Bayer for acquiring licensing rights | €										€ 19
License Agreement Contractual Terms										15 years
Percentage Of Royalty										20.00%
Talon Therapeutics, Inc. [Member]
Long-term Purchase Commitment [Line Items]
Acquisition-related contingent obligations, less current portion							1,600,000							$ 1,600,000	1,400,000
Contingent value rights future cash payments							195,000,000							195,000,000				$ 195,000,000.0
SPI-2012 [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments														$ 1,900,000
Issuance (shares) | shares														318,750
Potential milestone achievement							$ 238,000,000							$ 238,000,000
Poziotinib [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
Milestone net sales achievement														$ 358,000,000
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Percentage of royalty on annual worldwide sales under condition one							20.00%							20.00%
Percentage of royalties on net sale of licensed products														20.00%
Minimum [Member] | FOLOTYN [Member]
Long-term Purchase Commitment [Line Items]
Amount of annual worldwide sales on which royalty is payable under condition two														$ 150,000,000
Amount of annual worldwide sales on which royalty is payable under condition three														300,000,000
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Acquisition-related contingent obligations, less current portion							$ 6,000,000							6,000,000	$ 5,200,000
Maximum [Member] | FOLOTYN [Member]
Long-term Purchase Commitment [Line Items]
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														$ 300,000,000
INDIA | ZEVALIN [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
License Agreement Contractual Terms					15 years
Up-front non-refundable payment					$ 500,000
Recognition period for upfront payment														10 years
Licenses Revenue														$ 3,000,000
Percentage Of Royalty														20.00%
Allergan [Member]
Long-term Purchase Commitment [Line Items]
Up-front non-refundable payment													$ 41,500,000
License fee													$ 300,000
Allergan [Member] | Common Class A
Long-term Purchase Commitment [Line Items]
Common stock issued (shares) | shares													25,000
Stock issued													$ 100,000
Nippon Kayaku [Member]
Long-term Purchase Commitment [Line Items]
Upfront fee												$ 15,000,000
Payment related to agreement														$ 10,000,000
Payment on achievement of commercialization milestones														126,000,000
TopoTarget [Member]
Long-term Purchase Commitment [Line Items]
Potential milestone achievement							$ 278,000,000							$ 278,000,000
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%
Additional payments based on the achievement of certain development									$ 10,000,000
Aggregate payout value																$ 17,800,000
Second milestone payment																	$ 25,000,000
Principal executive office [Member] | Nevada [Member]
Long-term Purchase Commitment [Line Items]
Facility lease, non-cancelable operating lease expiring date														Apr. 30, 2019
Research and development facility [Member] | California [Member]
Long-term Purchase Commitment [Line Items]
Facility lease, non-cancelable operating lease expiring date														May 31, 2019