Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Examination [Line Items]
Effective tax rate	36.20%	37.30%
Income tax expense	$ 9,964,000	$ 7,327,000
Valuation allowance	4,500,000
Excess tax benefits from stock compensation	$ 1,000,000
Earliest Tax Year [Member] | Federal Tax Jurisdiction [Member]
Income Tax Examination [Line Items]
Tax years subject to examination	2011
Latest Tax Year [Member] | Federal Tax Jurisdiction [Member]
Income Tax Examination [Line Items]
Tax years subject to examination	2014