Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Deferred tax valuation allowance	$ 63,170,000	$ 59,043,000
Deferred tax assets, increase in valuation allowance	4,100,000	$ 55,600,000
Operating loss carryforward, subject to expiration	135,000,000
Operating loss carryforwards not subject to expiration	$ 39,500,000
Federal statutory rate	21.00%	21.00%
Tax cuts and jobs act of 2017, incomplete accounting, provision to income tax expense in continuing operations		$ 23,600,000
Accrued interest or penalties recorded related to uncertain tax positions	$ 0	0
Unrecognized tax benefits	935,000	924,000	$ 846,000
Unremitted earnings	0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 174,500,000	153,800,000
Net operating loss carryforwards expiration year	2027
Federal | Research Credit Carryforwards
Operating Loss Carryforwards [Line Items]
Research credit carryforwards	$ 2,500,000	2,200,000
Research credit carryforwards expiration year	2027
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 140,100,000	119,900,000
Net operating loss carryforwards expiration year	2032
State | Research Credit Carryforwards
Operating Loss Carryforwards [Line Items]
Research credit carryforwards	$ 1,200,000	$ 1,100,000
Research credit carryforwards expiration year	2022