Changes in Stock Options (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock Options, Exercised	3,700	30,500
Number of Stock Options, Cancelled	600	8,000
Number of Stock Options, Forfeited	21	21
Weighted Average Base Price, Exercised	$ 6.63	$ 8.26
Weighted Average Base Price, Cancelled	$ 7.60	$ 10.69
Weighted Average Base Price, Forfeited	$ 8.41	$ 8.41
Weighted Average Fair Value, Exercised	$ 5.08	$ 6.30
Weighted Average Fair Value, Cancelled	$ 5.75	$ 8.25
Weighted Average Fair Value, Forfeited	$ 4.96	$ 4.96