CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Product revenue, net	$ 306,486	$ 251,247	$ 159,201
Operating expenses:
Cost of sales	5,504	5,215	3,554
Research and development	89,017	75,247	40,376
Selling, general and administrative	100,359	81,289	62,416
Total operating expenses	194,880	161,751	106,346
Income from operations	111,606	89,496	52,855
Interest and other income (expense), net	5,070	2,657	(49)
Income before income taxes	116,676	92,153	52,806
Income tax expense (benefit)	22,495	16,743	(76,316)
Net income	94,181	75,410	129,122
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments, net of tax impact of $(104), $22 and $0, respectively	327	5	(75)
Foreign currency translation gain, net of tax	4
Total comprehensive income	$ 94,512	$ 75,415	$ 129,047
Basic net income per share (in dollars per share)	$ 0.82	$ 0.65	$ 1.14
Diluted net income per share (in dollars per share)	$ 0.77	$ 0.60	$ 1.04
Weighted average shares outstanding used in computing net income per share
Basic (in shares)	114,349	115,343	113,527
Diluted (in shares)	122,566	126,688	124,515