Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (78,096)	$ (84,510)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	203	(392)
Comprehensive loss	(77,893)	(84,902)
Comprehensive (income) loss attributable to noncontrolling interest	(60)	332
Total comprehensive loss attributable to Portola	$ (77,953)	$ (84,570)