Weighted-Average Assumptions Used to Estimate Grant Date Fair Values for Stock Options Granted (Detail) (Employee Stock Option)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Employee Stock Option
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Volatility	40.90%	48.86%	41.36%	48.85%
Expected term (in years)	5 years	5 years	5 years	5 years
Dividend yield	0.87%	1.22%	0.89%	1.21%
Risk-free interest rate	0.70%	0.88%	0.70%	0.88%