Organization and Summary of Significant Accounting Policies - Additional Information (Detail) shares in Millions			9 Months Ended	12 Months Ended
	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) Reporting_Unit Customer shares	Dec. 31, 2018 USD ($) Customer shares	Dec. 31, 2017 shares
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities				$ 1,603,981,000	$ 1,918,239,000
Senior secured notes				250,000,000.0
Contract with customer, asset, reclassified to receivable				12,800,000	24,200,000
Net expense reimbursements from collaboration partner				$ 24,000,000.0	$ 19,000,000.0
Number of customers accounted for major accounts receivable | Customer				3	3
Percentage of accounts receivable customers one				65.00%	44.00%
Percentage of accounts receivable customers two				17.00%	36.00%
Percentage of accounts receivable customers three				14.00%	12.00%
Number of reporting unit evaluated for goodwill | Reporting_Unit				1
Customer payment period from receipt of invoice				30 days
Weighted-average of potentially dilutive securities (stock options and RSUs) included in calculation of diluted securities under treasury stock method | shares					10.5
Other comprehensive income (loss), tax			$ 1,300,000
Operating lease right-of-use assets				$ 134,177,000	$ 0
Operating lease, liability				$ 155,246,000
Deferred rent					$ 9,300,000
Accounting Standards Update 2016-02
Organization And Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 83,500,000
Operating lease, liability	96,200,000
Cumulative effect on retained earnings, net of tax	$ 0
ASC 606
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings		$ 12,700,000
Reduction of deferred revenue		(2,000,000.0)
ASC 606 | Royalty | Calculated under Revenue Guidance in Effect before Topic 606
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings		$ 10,700,000
Shares of Common Stock Underlying Outstanding Stock Options
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share | shares					3.3
Stock Options and Restricted Stock Units
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share | shares				17.9		20.6
Manufacturing equipment | Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				3 years
Manufacturing equipment | Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				10 years
Buildings
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				20 years