Organization and Summary of Significant Accounting Policies (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Jan. 01, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization and Business
Number of operating segments | item			1
Concentrations of Credit Risk
Number of issuer to which company limits the amount of credit exposure other than US Government guaranteed securities | item			1
Number of financial investment to which company limits the amount of credit exposure other than US Government guaranteed securities | item			1
Accounts Receivable
Allowance for doubtful accounts			$ 0	$ 0
Impairment of Long-Lived Assets
Write-off of the acquired IPR&D		$ 12,000	$ 12,000
Revenue Recognition
Percentage of Medicare Part D insurance coverage gap mandate to be funded by manufacturers			50.00%
Categories of milestone events, number | item			3
Number of stages of life-cycle drugs | item			3
Stock-Based Compensation
Stock compensation expense			$ 133,100	96,200	$ 69,900
Recent Accounting Pronouncements
Deferred tax assets			847,716	868,382
Income tax (benefit) expense			$ 852	$ 3,182	$ 1,025
ASU No. 2016-16
Recent Accounting Pronouncements
Deferred tax assets	$ 34,900
Reversal of long-term prepaid taxes	(2,100)
Income tax (benefit) expense	$ 2,100
JAKAFI
Inventory
Shelf life for finished goods inventory, maximum			36 months
ICLUSIG
Inventory
Shelf life for finished goods inventory, maximum			24 months
ICLUSIG | Licensed IP
Revenue Recognition
Amortization period			12 years 6 months