Description of Business, Basis of Presentation, and Operating Segment (Details) $ in Millions		3 Months Ended
	Mar. 01, 2019 USD ($) product	Mar. 31, 2019 USD ($) Segment product
Segment Reporting Information [Line Items]
Number of late stage development products | product		2
Number of products | product	7
Potential payments based on achievement of sales milestones		$ 325.0
Number of reportable operating segment | Segment		1
Spectrum Pharma Canada [Member]
Segment Reporting Information [Line Items]
Ownership interest, percentage		50.00%
FUSILEV, FOLOTYN, ZEVALIN, MARQIBO, BELEODAQ, EVOMELA, and KHAPZORY [Member] | Acrotech Biopharma LLC [Member]
Segment Reporting Information [Line Items]
Disposal group, including discontinued operation, consideration	$ 158.8
Escrow deposits related to property sales	4.0
Aggregate amount receivable based on achievement of milestones	140.0
Payments receivable based on achievement of regulatory milestones	40.0
Potential payments based on achievement of sales milestones	$ 100.0