Summary of Significant Accounting Policies and Use of Estimates - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in retained earnings due to revenue recognition	$ (599,886)		$ (502,107)
Cash and equivalents maturities period	3 months
FUSILEV, MARQIBO, and BELEODAQ [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of months after expiration customers are allowed to return products	6 months
EVOMELA [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of months after expiration customers are allowed to return products	12 months
Number of months prior to product expiration during which customer can return product	6 months
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in retained earnings due to revenue recognition	$ (3,087)	$ 4,700