Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 Entity	Dec. 31, 2013 USD ($)
Income Tax [Line Items]
Valuation allowance	$ 48,319,000	$ 34,846,000		$ 21,293,000
Number of variable interest entities | Entity			6
Recognized intangible assets		$ 0
Amortization of intellectual property		15 years
Period of change in ownership	3 years
Percentage of change in ownership	50.00%
Unrecognized tax benefits, income tax penalties and interest accrued	$ 0	$ 0		$ 0
Change in unrecognized tax benefits	0
California [Member] | Operating Loss Carryforwards Expire in 2016 [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 200,000
Net operating loss carryforwards expiration year	2016
California [Member] | Operating Loss Carryforwards Expire in 2017 [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 1,400,000
Net operating loss carryforwards expiration year	2017
California [Member] | Operating Loss Carryforwards Expiring from 2028 through 2034 [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 47,300,000
Federal [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 65,400,000
Net operating loss carryforwards expiration year	2025
Research and development credit carryforward	$ 1,800,000
Research and development credit carryforward expiration year	2026
Federal [Member] | Orphan Drug Credits [Member]
Income Tax [Line Items]
Research and development credit carryforward	$ 2,900,000
Research and development credit carryforward expiration year	2035
State [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 48,900,000
Net operating loss carryforwards expiration year	2016
Research and development credit carryforward	$ 1,900,000
Foreign [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 5,800,000
Minimum [Member] | California [Member] | Operating Loss Carryforwards Expiring from 2028 through 2034 [Member]
Income Tax [Line Items]
Net operating loss carryforwards expiration year	2028
Maximum [Member] | California [Member] | Operating Loss Carryforwards Expiring from 2028 through 2034 [Member]
Income Tax [Line Items]
Net operating loss carryforwards expiration year	2034