Commitments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule Of Contractual Commitments [Line Items]      
Expiration of operating lease agreements Through 2018    
Expiration of other contractual obligations Through 2016    
Rent expense $ 1.9 $ 1.9 $ 2.0