Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Income Taxes Disclosure [Line Items]
Operating Loss Carryforwards	$ 81.2
Equity Method Investment, Ownership Percentage	50.00%
Operating Loss Carryforward Of Expiration Year	2034
Additional Paid-In Capital [Member]
Income Taxes Disclosure [Line Items]
Operating Loss Carryforwards	81.2
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	2.5
Research Tax Credit Carryforward [Member]
Income Taxes Disclosure [Line Items]
Tax Credit Carryforward, Amount	1.6
State and Local Jurisdiction [Member]
Income Taxes Disclosure [Line Items]
Operating Loss Carryforwards	4.1
Operating Loss Carryforward Of Expiration Year	2034
Tax Credit Carryforward, Amount	$ 0.9