Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands, shares in Millions		3 Months Ended								12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2018 USD ($) Customer	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) Customer	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) Customer Reporting_Unit shares	Dec. 31, 2017 USD ($) Customer shares	Dec. 31, 2016 USD ($) shares
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities		$ 1,918,239				$ 353,220				$ 1,918,239	$ 353,220
Senior secured notes		$ 250,000								$ 250,000
Senior secured notes, maturity date										Oct. 05, 2020
Contract with customer, asset, reclassified to receivable										$ 24,200	3,300
Net expense reimbursements from collaboration partner										$ 19,000	$ 1,700
Number of customers accounted for major accounts receivable | Customer		3				4				3	4
Percentage of accounts receivable customers one										44.00%	43.00%
Percentage of accounts receivable customers two										36.00%	20.00%
Percentage of accounts receivable customers three										12.00%	19.00%
Percentage of accounts receivable customers four											14.00%
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
Minimum percentage of amount realized upon ultimate settlement										50.00%
Revenue recognized from contracts with customers		$ 39,826	$ 27,762	$ 1,087,717	$ 38,018	$ 95,466	$ 152,928	$ 34,589	$ 24,728	$ 1,193,323	$ 307,711	$ 165,436
Deferred rent		9,300				6,000				9,300	6,000
Royalty [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenue recognized from contracts with customers										41,976	$ 33,527	$ 19,542
ASC 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings	$ 12,700
Reduction of deferred revenue	(2,000)
ASC 606 [Member] | MOVANTIK and ADYNOVATE [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenue recognized from contracts with customers					$ 11,100	$ 9,600
Type of Revenue [Extensible List]					us-gaap:RoyaltyMember	us-gaap:RoyaltyMember
ASC 606 [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenue recognized from contracts with customers										1,183,911
ASC 606 [Member] | Royalty [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings	10,700
Revenue recognized from contracts with customers										$ 41,690
ASC 606 [Member] | Royalty [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | MOVANTIK and ADYNOVATE [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings	$ 10,700
Stock Options and Restricted Stock Units [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share | shares											20.6	19.9
Shares of Common Stock Underlying Outstanding Stock Options [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share | shares										3.3
Minimum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset		87,000								$ 87,000
Operating Lease, Liability		96,000								96,000
Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset		97,000								97,000
Operating Lease, Liability		$ 106,000								$ 106,000
Buildings [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives										20 years
Manufacturing Laboratory and Other Equipment [Member] | Minimum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives										3 years
Manufacturing Laboratory and Other Equipment [Member] | Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives										10 years