Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (71,177)	$ (82,941)	$ (261,658)	$ (194,119)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities, net of tax	237	33	(28)	(25)
Comprehensive loss	(70,940)	(82,908)	(261,686)	(194,144)
Comprehensive (income) loss attributable to noncontrolling interest (SRX Cardio)	(126)	5	(17)	(190)
Total comprehensive loss attributable to Portola	$ (71,066)	$ (82,903)	$ (261,703)	$ (194,334)