Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($)		1 Months Ended	6 Months Ended
		Dec. 31, 2015	Jun. 30, 2016	Dec. 01, 2015
Asset Acquisition [Line Items]
Restricted cash (Development Partner)	[1]	$ 341,000	$ 145,000
Development Partner
Asset Acquisition [Line Items]
Variable interest entity, Terms of arrangements			Accordingly, the Development Partner is subject to consolidation and we have consolidated the financial statements of the Development Partner since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; (b) allocating loss attributable to the noncontrolling interest in the Development Partner 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		$ 500,000
Fair value of indefinite lived intangible assets				$ 3,200,000
Noncontrolling interest in variable Interest entity				$ 2,900,000
Restricted cash (Development Partner)			$ 145,000
Net loss attributable to noncontrolling interest (Development Partner)			$ 0

[1] Amounts include the assets and liabilities of our Development Partner 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.