Income Taxes - Summary of Statutory Federal Tax Rate to Income or Loss before Taxes (Detail)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal tax benefit at statutory rate	34.00%	34.00%	34.00%
Change in valuation allowance	(3.00%)	(8.00%)	(23.00%)
Research and development credits	4.00%	2.00%	2.00%
Non-deductible warrant			(7.00%)
Foreign loss not benefitted	(30.00%)	(27.00%)	(5.00%)
Other Non-deductible expenses	(5.00%)	(2.00%)	(1.00%)
Total	0.00%	0.00%	0.00%

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

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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-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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