Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Weighted-Average Estimated Fair Value Per Share of Options Granted under Plans (Detail)

v2.4.0.6
Share-Based Compensation - Weighted-Average Estimated Fair Value Per Share of Options Granted under Plans (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]      
Weighted-Average Estimated Fair Value Per Share of Options Granted $ 5.40 $ 6.23