Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of the income tax expense/(benefit)
U.S. corporate income tax rate (as a percent)	21.00%	35.00%
Current
Federal	$ 26,772	$ 18,288	$ 544
State	5,621	3,822	78
Deferred
Federal	(2,450)	21,493	(39,898)
State	(760)	(269)	(1,576)
Income tax expense/ (benefit)	29,183	43,334	(40,852)
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
Income tax expense computed at U.S. Federal statutory income tax rate	29,437	35,217	17,629
State income taxes	3,674	2,714	(1,523)
Permanent items	(2,196)	(2,311)	715
Research and development credits	(3,199)	(2,196)	(1,902)
Uncertain income tax position	716	(1,137)	143
Effect of rate changes		9,694
Change in valuation allowance			(56,019)
Other	751	1,353	105
Income tax expense (benefit)	29,183	43,334	(40,852)
NOLs utilized	18,400
Research and development credit carryforwards	4,200
Deferred tax assets:
Convertible bond hedge	21,412
Accrued sales deductions	13,205	8,449
Accrued compensation and stock based compensation	8,218	7,090
Non-recourse liability related to sale of future royalties	5,571	6,377
Research and development credits carryforwards	3,817	3,795
Amortization	3,289	2,073
Net operating loss carryforwards	2,900	5,072
Deferred rent	125	211
Inventory	499	480
Alternative Minimum Tax (AMT) credit	978	1,613
Other	1,143	645
Total deferred tax assets	61,157	35,805
Less: valuation allowance	(9)
Deferred tax asset, net of valuation allowance	61,148	35,805
Deferred tax liability:
Debt discount on 2023 Notes	(17,568)
Infringement legal costs	(10,697)	(10,557)
Depreciation	(236)	(264)
Section 481(a)	(2,964)	(4,141)
Net deferred tax assets	29,683	20,843
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at the beginning of the period	8,859	9,299	9,341
Gross increases related to current-year tax positions	1,108	1,178	662
Gross decreases related to current-year tax positions			(169)
Gross increases related to prior-year tax positions		947
Gross decreases related to prior-year tax positions	(484)		(375)
Lapse of statute of limitations	(635)
Change in tax rates		(2,565)	(160)
Balance at the end of the period	8,848	8,859	9,299
Alternate minimum tax expense on uncertain tax position	600	$ 0	$ 500
Current tax benefit	600
Tax expense on uncertain tax position	300
U.S. Federal
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
NOL carryforwards	20,600
State
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
NOL carryforwards	$ 9,200