Description of Business, Basis of Presentation, and Operating Segment - Additional Information (Details)	12 Months Ended
Dec. 31, 2017 Segment product
Accounting Policies [Abstract]
Number of products	6
Number of late stage development drugs	3
Number of reportable operating segment \| Segment	1
Spectrum Pharma Canada [Member]
Segment Reporting Information [Line Items]
Ownership interest, percentage	5000.00%

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=77990344&loc=SL6759159-111685

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration