Changes in Stock Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options exercised	173,208	18,725	180,923
Number of Options cancelled	8,229	109,236	37,312
Number of Options Forfeited	21
Weighted Average Base Price, exercised	$ 6.03	$ 8.06	$ 10.48
Weighted Average Base Price, cancelled	$ 10.62	$ 42.07	$ 315.18
Weighted Average Base Price, Forfeited	$ 8.41
Weighted Average Fair Value, Exercised	$ 4.83	$ 6.22	$ 9.13
Weighted Average Fair Value, Cancelled	$ 8.16	$ 36.36	$ 249.10
Weighted Average Fair Value, Forfeited	$ 4.96