Composition of Total Revenue - Schedule of Product Sales, Net by Geography (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Product sales, net	$ 25,845	$ 35,241
Percentage of product sales, net	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Product sales, net	$ 23,801	$ 33,779
Percentage of product sales, net	92.10%	95.90%
Europe (ZEVALIN only) [Member]
Segment Reporting Information [Line Items]
Product sales, net	$ 2,044	$ 1,462
Percentage of product sales, net	7.90%	4.10%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration