Comparison of Reported Condensed Consolidated Statement of Operations Under New Guidance (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Collaboration and license revenue	$ 14,177	$ 3,828	$ 24,832	$ 12,743
Operating expenses:
Research and development	40,237	55,273	166,744	135,210
Loss from operations	(69,144)	(80,456)	(258,139)	(186,828)
Net loss	(71,177)	(82,941)	(261,658)	(194,119)
Net loss attributable to Portola	$ (71,303)	$ (82,936)	$ (261,675)	$ (194,309)
Basic and diluted	$ (1.08)	$ (1.41)	$ (3.97)	$ (3.38)
Collaboration and License Revenue
Revenues:
Collaboration and license revenue	$ 7,001	$ 3,828	$ 14,785	$ 12,743
Balances Without the Adoption of ASC 606 \| Accounting Standards Update 2014-09
Operating expenses:
Research and development	39,289		164,310
Loss from operations	(73,611)		(260,979)
Net loss	(75,644)		(264,498)
Net loss attributable to Portola	$ (75,770)		$ (264,515)
Basic and diluted	$ (1.15)		$ (4.02)
Balances Without the Adoption of ASC 606 \| Collaboration and License Revenue \| Accounting Standards Update 2014-09
Revenues:
Collaboration and license revenue	$ 1,586		$ 9,511
Effect of Change \| Accounting Standards Update 2014-09
Operating expenses:
Research and development	948		2,434
Loss from operations	4,467		2,840
Net loss	4,467		2,840
Net loss attributable to Portola	$ 4,467		$ 2,840
Basic and diluted	$ 0.07		$ 0.04
Effect of Change \| Collaboration and License Revenue \| Accounting Standards Update 2014-09
Revenues:
Collaboration and license revenue	$ 5,415		$ 5,274

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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