Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Detail)

v2.4.0.6
Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Common stock available for award under the plans 1,393,602
Additional share authorized under share based compensation 4,000,000
Minimum
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected volatility 33.00%
Expected dividend yield 0.00%
Correlation of movement of total shareholder return maximum range (67.00%)
Maximum
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected volatility 74.00%
Expected dividend yield 2.50%
Correlation of movement of total shareholder return maximum range 94.00%
LIBOR
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate, minimum 0.15%
Risk-free interest rate, maximum 0.72%
Total Shareholder Return
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Restricted share units TSR awards, range minimum 0.00%
Restricted share units TSR awards, range maximum 150.00%
Directors Compensation Plan
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Common stock available for award under the plans 546,829
Restricted Stock
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 43,687
Unrecognized share-based compensation expense 0.4
Recognition period for unrecognized compensation expense April 2015
Restricted Stock Units (RSUs)
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 959,698
Unrecognized share-based compensation expense 9.2
Recognition period for unrecognized compensation expense November 2014