Weighted Average Assumptions used to Determine Fair Values of Options Granted (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	40.00%	40.00%	40.00%	40.00%
Risk-free interest rate	1.54%	2.74%	1.54%	2.74%
Expected dividends	0.26%	0.26%	0.26%	0.26%
Weighted average fair value of options granted during period	$ 1.54	$ 2.00	$ 1.54	$ 2.00
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years 219 days	6 years 219 days	6 years 219 days	6 years 219 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	8 years 73 days	8 years 73 days	8 years 73 days	8 years 73 days