Assumptions Used in Determining Fair Value of Options Granted (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assumptions Disclosure [ Line Items]
Expected term of options in years	6 years 3 months 18 days	6 years 3 months 18 days
Expected volatility		42.80%
Expected volatility, maximum	42.50%
Expected volatility, minimum	41.50%
Risk-free interest rate		2.50%
Risk-free interest rate, maximum	2.30%
Risk-free interest rate, minimum	2.10%
Expected dividend yield	0.00%	0.00%