Financial Commitments & Contingencies And License Agreements - Additional Information (Detail) $ in Thousands, € in Millions		1 Months Ended															2 Months Ended	3 Months Ended					5 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Apr. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Aug. 31, 2017 USD ($)	Jul. 31, 2017 USD ($) shares	Apr. 30, 2016 USD ($) shares	Feb. 29, 2016	Jan. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Jun. 30, 2014	Feb. 28, 2014 USD ($)	Apr. 30, 2012 EUR (€)	Feb. 28, 2010 USD ($)	Nov. 30, 2009 USD ($)	Oct. 31, 2008 USD ($) shares	Jan. 31, 2016 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2017 USD ($) shares	Jun. 30, 2018 USD ($) Country	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) shares	Nov. 30, 2014 USD ($)	Jul. 17, 2013 USD ($)
Long-term Purchase Commitment [Line Items]
Potential payments based on achievement of sales milestones																								$ 325,000
Acquisition-related contingent obligations																		$ 6,755					$ 6,272	6,755
Total revenues																		24,168	$ 34,301					54,662	$ 63,402
Payment of all royalty fees			$ 2,600
Amount receivable on approval of oral form of FUSILEV																		200						200
Intangible assets																		305,668					$ 305,668	305,668
Additional license fees																								60,000
Common stock issued (shares) | shares					3,243,882																		10,314,250			10,890,915
Consideration paid for the rights granted (shares)												$ 1,000
Proceeds from common shares sold under an at-market-issuance sales agreement					$ 23,745																		$ 104,527			$ 73,869
Cash paid for income taxes																								27	10
Deferrals and contributions																		$ 6,000					11,000	$ 6,000
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%
EVOMELA distribution rights [Member]
Long-term Purchase Commitment [Line Items]
Intangible assets						$ 7,700												$ 7,700					7,700	$ 7,700
ZEVALIN, FOLOTYN, BELEODAQ, And MARQIBO [Member]
Long-term Purchase Commitment [Line Items]
Payments receivable on achievement of potential regulatory milestones																								2,000
Total consideration received																				$ 6,000
Regulatory [Member]
Long-term Purchase Commitment [Line Items]
Receivable for contracted sales and marketing services				$ 2,000
Total Consideration [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received																	$ 18,000
Payment One [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received									$ 15,000
Payment Two [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total consideration received								$ 3,000
Ligand Pharmaceuticals Inc [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments						6,000
ZEVALIN [Member]
Long-term Purchase Commitment [Line Items]
Potential payments based on achievement of sales milestones																								5,000
Acquisition-related contingent obligations																		100					100	$ 100
ZEVALIN [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
Fees paid to Bayer for acquiring licensing rights | €													€ 19
Minimum number of countries outside U.S. approved ZEVALIN for treatment | Country																								40
Percentage of royalty							20.00%
License agreement contractual terms							15 years
Payments receivable on achievement of potential sales milestones																		1,500						$ 1,500
Payments receivable on achievement of potential regulatory milestones																								1,500
Aggregate amount receivable based on achievement of milestones																								3,000
Talon Therapeutics, Inc. [Member]
Long-term Purchase Commitment [Line Items]
Acquisition-related contingent obligations																		6,700					$ 6,200	6,700
Contingent value rights future cash payments																		$ 195,000						195,000				$ 195,000
SPI-2012 [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments						$ 2,700
Issuance (shares) | shares						318,750
Proceeds from common shares sold under an at-market-issuance sales agreement						$ 2,300
Cash paid for income taxes						$ 400
Spi Two Thousand Twelve [Member]
Long-term Purchase Commitment [Line Items]
Potential payments based on achievement of sales milestones																								225,000
Potential payments based on achievement of regulatory milestones																								13,000
Poziotinib [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
Potential payments based on achievement of regulatory milestones																								$ 33,000
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
Amount of annual worldwide sales on which royalty is payable under condition three																								300,000
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
Amount of annual worldwide sales on which royalty is payable under condition two																								300,000
Maximum [Member] | Regulatory [Member]
Long-term Purchase Commitment [Line Items]
Potential milestone payments																								16,000
Maximum [Member] | Commercial progress and sales-dependent [Member]
Long-term Purchase Commitment [Line Items]
Potential milestone payments																								$ 107,000
INDIA [Member] | ZEVALIN [Member] | Licensing Agreements [Member]
Long-term Purchase Commitment [Line Items]
Percentage of royalty																								20.00%
License agreement contractual terms											15 years
Up-front non-refundable payment										$ 500
Allergan [Member]
Long-term Purchase Commitment [Line Items]
Up-front non-refundable payment																$ 41,500
Allergan [Member] | Common Class A
Long-term Purchase Commitment [Line Items]
Common stock issued (shares) | shares																25,000
Stock issued, value																$ 100
Nippon Kayaku [Member]
Long-term Purchase Commitment [Line Items]
Payments receivable on achievement of potential regulatory milestones																								$ 10,000
Upfront fee															$ 15,000
Payment on achievement of commercialization milestones																								126,000
TopoTarget [Member]
Long-term Purchase Commitment [Line Items]
Payments receivable on achievement of potential sales milestones																		$ 190,000						190,000
Payments receivable on achievement of potential regulatory milestones																								$ 88,000
Payment of all royalty fees														$ 30,000
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
Aggregate payout value																						$ 17,800
Second milestone payment																											$ 25,000
Restatement Adjustment [Member] | EVOMELA distribution rights [Member]
Long-term Purchase Commitment [Line Items]
Intangible assets																		(7,700)						$ (7,700)
License and Service [Member]
Long-term Purchase Commitment [Line Items]
Total revenues																		$ 415	$ 3,145					$ 2,799	$ 6,401
License and Service [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total revenues		$ 2,000
License and Service [Member] | Total Consideration [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total revenues																					$ 15,000
License and Service [Member] | Payment Two [Member] | Zevalin Rights [Member]
Long-term Purchase Commitment [Line Items]
Total revenues	$ 3,000
License and Service [Member] | Maximum [Member] | Regulatory [Member]
Long-term Purchase Commitment [Line Items]
Total revenues				$ 3,000
License [Member] | Allergan [Member]
Long-term Purchase Commitment [Line Items]
License fee																$ 300
MD Anderson [Member]
Long-term Purchase Commitment [Line Items]
Potential payments based on achievement of sales milestones		23,000
Payment of all royalty fees		500
Potential payments based on achievement of regulatory milestones		$ 11,000