Reconciliation of Expected Income Tax Benefit (Detail)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax computed at federal statutory tax rate	34.00%	34.00%	34.00%
State taxes, net of federal benefit	5.30%	5.30%	5.10%
Research and development credits	2.00%	2.60%	2.00%
Other permanent differences	(2.00%)	(0.80%)	(0.90%)
Foreign rate differential	(0.10%)	0.00%	(0.20%)
Permanent difference – estimated settlement liability	(9.10%)	(0.00%)	(0.00%)
Other	(3.80%)	(5.70%)	(0.50%)
Change in valuation allowance	(26.30%)	(35.40%)	(39.50%)
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=6907707&loc=d3e32698-109319

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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.

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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 statutory income tax expense (benefit) outside of the country of domicile.

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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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