Stock Compensation - Weighted-Average Assumptions for Determining Fair Value of Options Granted (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	1.35%	1.79%	1.42%	1.76%
Expected term (years)	5 years	5 years	5 years	5 years
Expected stock volatility	36.17%	58.62%	36.42%	64.98%
Dividend yield	0.72%		0.74%