Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (49,627)	$ (71,177)	$ (196,200)	$ (261,658)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	(6)	237	355	(28)
Foreign currency translation adjustment	117	0	75	0
Comprehensive loss	(49,516)	(70,940)	(195,770)	(261,686)
Comprehensive (income) loss attributable to noncontrolling interest	0	(126)	2,213	(17)
Total comprehensive loss attributable to Portola	$ (49,516)	$ (71,066)	$ (193,557)	$ (261,703)