Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands		Total		IPO	Follow-on Offering	Convertible Preferred Stock	Common Stock	Common Stock IPO	Common Stock Follow-on Offering	Additional Paid-In Capital	Additional Paid-In Capital IPO	Additional Paid-In Capital Follow-on Offering	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest (Development Partner)
Balance at beginning of year at Dec. 31, 2012		$ (191,569)				$ 317,280	$ 1			$ 10,717			$ (202,320)	$ 33
Balance at beginning of year (in shares) at Dec. 31, 2012						24,026,797	1,385,508
Exercise of employee stock options for cash		2,529								2,529
Exercise of employee stock options for cash (in shares)							403,468
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)							500
Lapse of repurchase rights related to common shares issued pursuant to early exercises		4								4
Conversion of preferred stock warrants to common stock warrants		659								659
Conversion of preferred stock to common stock (in shares)						(24,026,797)	24,026,797
Conversion of preferred stock to common stock		317,280				$ (317,280)	$ 24			317,256
Issuance of stock (in shares)								9,686,171	5,412,686
Issuance of stock				$ 125,872	$ 119,975			$ 11	$ 5		$ 125,861	$ 119,970
Employee stock-based compensation expense		4,140								4,140
Compensation expense relating to stock options granted to consultants		775								775
Unrealized gain on available-for-sale securities, net of tax		22												22
Net loss		(83,352)											(83,352)
Balance at end of the year at Dec. 31, 2013		296,335					$ 41			581,911			(285,672)	55
Balance at end of the year (in shares) at Dec. 31, 2013							40,915,130
Exercise of employee stock options for cash		4,399					$ 1			4,398
Exercise of employee stock options for cash (in shares)							652,125
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)							500
Lapse of repurchase rights related to common shares issued pursuant to early exercises		4								4
Issuance of common stock upon cashless exercise of common stock warrants (shares)							40,314
Issuance of common stock pursuant to ESPP purchase (in shares)							28,737
Issuance of common stock pursuant to ESPP purchase		579								579
Issuance of stock (in shares)								7,130,000
Issuance of stock				174,621				$ 7			174,614
Employee stock-based compensation expense		8,514								8,514
Compensation expense relating to stock options granted to consultants		769								769
Unrealized gain on available-for-sale securities, net of tax		(294)												(294)
Net loss		(137,125)											(137,125)
Balance at end of the year at Dec. 31, 2014		347,802					$ 49			770,789			(422,797)	(239)
Balance at end of the year (in shares) at Dec. 31, 2014							48,766,806
Balance at end of the year at Dec. 31, 2014		347,802
Exercise of employee stock options for cash		$ 11,111					$ 1			11,110
Exercise of employee stock options for cash (in shares)		1,095,486					1,095,486
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)							125
Issuance of common stock upon cashless exercise of common stock warrants (shares)							3,041
Issuance of common stock pursuant to ESPP purchase (in shares)							30,307
Issuance of common stock pursuant to ESPP purchase		$ 837					$ 1			836
Issuance of stock (in shares)								6,463,750
Issuance of stock				$ 271,096				$ 6			$ 271,090
Employee stock-based compensation expense		20,172								20,172
Compensation expense relating to stock options granted to consultants		2,794								2,794
Unrealized gain on available-for-sale securities, net of tax		89												89
Consolidation of variable interest entity		2,927													$ 2,927
Net loss		(226,505)											(226,505)
Balance at end of the year at Dec. 31, 2015	[1]	427,396
Balance at end of the year (in shares) at Dec. 31, 2015							56,359,515
Balance at end of the year at Dec. 31, 2015		$ 430,323	[1]				$ 57			$ 1,076,791			$ (649,302)	$ (150)	$ 2,927

[1] Amounts include the assets and liabilities of 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 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.