Income Taxes - Reconciliation of Federal Statutory Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	34.00%	34.00%	34.00%
State taxes, net of federal benefit	2.88%	3.45%	3.45%
Stock compensation	(0.61%)
Permanent differences-derivative loss			(9.10%)
Permanent differences-other	(1.00%)	(4.66%)	2.24%
Research and development ("R&D") credit	0.98%	0.95%	2.73%
Other	(0.47%)	0.64%	0.61%
Increase in valuation allowance	(35.78%)	(34.38%)	(33.93%)
Federal statutory income tax rate, Total	0.00%	0.00%	0.00%

Effective income tax rate reconciliation permanent differences.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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