Description of Business, Basis of Presentation, and Operating Segment - Additional Information (Details) $ in Millions		12 Months Ended
	Jan. 17, 2019 USD ($) employee	Dec. 31, 2018 Segment product
Accounting Policies [Abstract]
Number of products | product		7
Number of late stage development drugs | product		2
Number of reportable operating segment | Segment		1
Spectrum Pharma Canada [Member]
Segment Reporting Information [Line Items]
Ownership interest, percentage		5000.00%
Subsequent Event [Member] | FUSILEV, FOLOTYN, ZEVALIN, MARQIBO, BELEODAQ, EVOMELA, and KHAPZORY [Member] | Acrotech Biopharma LLC [Member]
Segment Reporting Information [Line Items]
Upfront payment expected to be received	$ 160
Consideration held in escrow for six months	$ 4
Period consideration is held in escrow	6 months
Payment receivable on achievement of regulatory milestones	$ 140
Reduction in employees, number of employees | employee	90