Reconciliation Between Effective Tax Rate and Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal income tax rate	34.00%	34.00%	34.00%
Research and development tax credits	2.40%	1.40%	(0.60%)
Valuation allowance	(21.60%)	(12.40%)	(7.50%)
Permanent Differences	(2.40%)	(8.80%)	(25.90%)
Foreign rate differential	(12.40%)	(14.20%)
Effective tax rate	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.

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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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