Summary of Information Regarding Option Activity (Parenthetical) (Detail)	Dec. 31, 2012
Awards Granted to Non-Executive Level Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rates	8.00%
Awards Granted to Executive Level Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rates	3.00%