Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Additional Information (Detail)

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Intangible Assets - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]      
Amortization expense for intangibles $ 15.8us-gaap_AmortizationOfIntangibleAssets $ 4.9us-gaap_AmortizationOfIntangibleAssets $ 2.3us-gaap_AmortizationOfIntangibleAssets