Summary of Significant Accounting Policies - Additional Information (Detail)		9 Months Ended
	Jun. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jan. 01, 2015 Subsidary
Summary Of Significant Accounting Policies [Line Items]
Marketable Securities, Realized Gain (Loss)		$ 0	$ 0
Impairments of long-lived assets		0	$ 0
Number of subsidiary corporations owned | Subsidary				7
Interest or penalties charged in relation to the unrecognized tax benefits.		0
CPRIT | Maximum
Summary Of Significant Accounting Policies [Line Items]
Research grant contract amount	$ 19,800,000	$ 19,800,000