Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended	9 Months Ended
		Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2016	Sep. 30, 2016	Dec. 01, 2015
Asset Acquisition [Line Items]
Restricted cash (SRX Cardio)	[1]	$ 1,930,000	$ 341,000	$ 1,930,000	$ 1,930,000
Net income attributable to noncontrolling interest (SRX Cardio)				1,853,000	$ 1,853,000
SRX Cardio
Asset Acquisition [Line Items]
Variable interest entity, Terms of arrangements					Accordingly, SRX Cardio is subject to consolidation and we have consolidated the financial statements of SRX Cardio since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; and (b) allocating loss attributable to the noncontrolling interest in SRX Cardio to net loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet.
Variable interest entity, Upfront payment		2,200,000	$ 500,000
Fair value of indefinite lived intangible assets						$ 3,200,000
Noncontrolling interest in variable Interest entity						$ 2,900,000
Restricted cash (SRX Cardio)		$ 1,900,000		1,900,000	$ 1,900,000
SRX Cardio | License Agreement
Asset Acquisition [Line Items]
Notice period for agreement termination		90 days
SRX Cardio | License Agreement | Maximum
Asset Acquisition [Line Items]
Research and development milestone payment obligation		$ 152,500,000		$ 152,500,000	$ 152,500,000
Percentage of royalties on net sales, obligated to pay		6.00%
SRX Cardio | License Agreement | Minimum
Asset Acquisition [Line Items]
Percentage of royalties on net sales, obligated to pay		2.00%

[1] Amounts include the assets and liabilities of SRX Cardio, LLC, a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 7, “Asset Acquisition and License Agreements,” to these condensed consolidated financial statements.