Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Cumulative change in ownership	50.00%
Period of cumulative ownership change	3 years
Recognized deferred tax assets for net operating losses	$ 11,100,000
Federal research and development credits	1,200,000	$ 12,700,000
State research and development credits	1,200,000	12,700,000
Deferred tax assets for foreign net operating loss	28,000
Deferred tax assets valuation allowance	127,341,000	$ 69,144,000
Deferred tax assets change in valuation allowance	58,200,000
Unrecognized tax benefits that would not impact effective tax rate	4,300,000
California | Research Tax Credits
Income Tax [Line Items]
Tax credit carryforwards	$ 700,000
California | Minimum
Income Tax [Line Items]
Tax year open for examination	2012
California | Maximum
Income Tax [Line Items]
Tax year open for examination	2016
Federal
Income Tax [Line Items]
Research and development credits	$ 400,000
Net operating loss carryforwards	$ 100,000,000
Net operating loss carryforwards expiration date	2024
Federal | Research Tax Credits
Income Tax [Line Items]
Tax credit carryforwards	$ 1,700,000
Tax credit carryforward expiration period	2026
Federal | Minimum
Income Tax [Line Items]
Tax year open for examination	2013
Federal | Maximum
Income Tax [Line Items]
Tax year open for examination	2016
State
Income Tax [Line Items]
Research and development credits	$ 400,000
Net operating loss carryforwards	$ 60,000,000
Net operating loss carryforwards expiration date	2030
State | Research Tax Credits
Income Tax [Line Items]
Tax credit carryforward expiration period	2029
Foreign
Income Tax [Line Items]
Net operating loss carryforwards	$ 200,000
Net operating loss carryforwards expiration date	2023