Income Taxes - Reconciliation of Federal Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory federal income tax (benefit) rate	(34.00%)	(34.00%)	(34.00%)
State income tax (benefit) rate			(3.30%)
Increase resulting from:
Expenses not deductible for taxes	0.80%	0.50%	8.80%
Increase in valuation allowance	32.60%	38.80%	3.70%
Change in state deferred tax rate	0.00%	1.10%	17.70%
Change in foreign deferred tax rate	2.80%	0.90%	1.80%
Expiration of tax attributes	1.70%	0.50%	5.30%
Prior year true up	1.10%	(0.70%)
Tax credits	(2.40%)	(3.00%)
Warrant valuation	(2.50%)	(4.10%)
Effective tax (benefit) rate	0.00%	0.00%	0.00%

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Effective income tax rate reconciliation expiration of tax attributes.

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Effective income tax rate reconciliation state deferred tax rate differential.

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Effective Income Tax Rate Reconciliation Warrants

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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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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 revisions of previously reported income tax expense.

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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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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 tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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