Income Taxes - Reconciliation of Expected Income Tax Benefit (Expense) Computed using Federal Statutory Income Tax Rate Effective Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation:
Income tax benefit computed at federal statutory tax rate	34.00%	34.00%	34.00%
State taxes, net of federal benefit	5.05%	4.67%	5.19%
Change in valuation allowance	(39.09%)	(39.43%)	(39.88%)
General business credits and other credits	1.33%	4.28%	0.86%
Permanent differences	(1.29%)	(3.52%)	(0.17%)
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.

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-Publisher FASB

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- Definition

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 state and local income tax expense (benefit), net of federal tax expense (benefit).

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