Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Cash equivalents maturities, term	three months or less
Accumulated deficit	$ (278,463)	$ (264,809)
Cash and short-term investments	$ 12,000
Substantial doubt about going concern, management's evaluation	Mateon's existing cash and short-term investments to support operations into October 2017. Prior to this time, the Company will need to secure additional funding or could be forced to curtail or terminate operations. Because the Company does not currently have a guaranteed source of working capital that will sustain operations past October 2017, Management has determined that there is substantial doubt about the Company's ability to continue as a going concern.
Substantial doubt about going concern	The Company will need to raise capital in order to fund its operations beyond this date. If the Company is unable to access additional funds when needed, it may not be able to continue the development of its investigational drugs and the Company could be required to delay, scale back or eliminate some or all of its development programs and other operations. Any additional equity financing, if available to the Company, may not be available on favorable terms, would most likely be dilutive to its current stockholders and debt financing, if available, and may involve restrictive covenants.
Minimum [Member]
Subsidiary, Sale of Stock [Line Items]
Estimated useful lives of the assets	3 years
Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Estimated useful lives of the assets	5 years