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Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 7.6us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount	$ 7.1us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Net operating loss carryforwards expiration year	2034
Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax year open to examination	2006
Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax year open to examination	2014
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	77.3us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_DomesticCountryMember
Federal [Member] | Research [Member]
Operating Loss Carryforwards [Line Items]
Research and development credit carryforwards	1.2us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_DomesticCountryMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember
Research and development tax credit carryforwards expiration year	2034
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	58.1us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember
State [Member] | Research [Member]
Operating Loss Carryforwards [Line Items]
Research and development credit carryforwards	$ 0.8us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember
Research and development tax credit carryforwards expiration year	2029

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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-Name Accounting Standards Codification

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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