Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Net operating loss carryforwards, federal	$ 111,400,000
Net operating loss carryforwards, state	110,600,000
Net operating loss carryforwards	45,488,000	$ 46,749,000
Valuation allowance	51,040,000	50,961,000
Valuation allowance change	79,000
Research and development credit carryforwards	3,355,000	2,462,000
Unrecognized tax benefits	0	$ 0
State
Income Taxes [Line Items]
Research and development tax credit carryforward	1,100,000
Canada Revenue Agency
Income Taxes [Line Items]
Operating loss carryforwards for Canadian federal taxes	7,800,000
Research and development credit carryforwards	2,900,000
Federal
Income Taxes [Line Items]
Research and development tax credit carryforward	1,900,000
Additional Paid-in Capital | State
Income Taxes [Line Items]
Net operating loss carryforwards	800,000
Investment Tax Credit Carryforward | Canada Revenue Agency
Income Taxes [Line Items]
Canadian federal investment tax credit carryforwards	723,000
Expiration date 2035 | Canada Revenue Agency
Income Taxes [Line Items]
Operating loss carryforwards for Canadian federal taxes	5,300,000
Expiration Date 2036 | Canada Revenue Agency
Income Taxes [Line Items]
Operating loss carryforwards for Canadian federal taxes	$ 2,500,000