Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Common stock available for award under the plans 5,393,602  
Additional share authorized under share based compensation 4,000,000  
Total Shareholder Return Performance Stock Awards
   
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 200.00%  
Directors Compensation Plan
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Common stock available for award under the plans 519,379  
Restricted Stock
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Shares granted, grant date fair value $ 0.3 $ 0.4
Shares vested, grant date fair value 0.4 0.5
Unrecognized share-based compensation expense 0.6  
Recognition period for unrecognized compensation expense 2016-04  
Restricted Stock Units (RSUs)
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Shares granted, grant date fair value 12.8 14.2
Unrecognized share-based compensation expense $ 16.1  
Recognition period for unrecognized compensation expense 2015-11  
Restricted Stock Units (RSUs) | LIBOR
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Risk-free interest rate, minimum 0.27% 0.15%
Risk-free interest rate, maximum 0.91% 0.72%
Restricted Stock Units (RSUs) | Minimum
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected volatility 30.00% 33.00%
Expected dividend yield 0.00% 0.00%
Correlation of movement of total shareholder return maximum range (84.00%) (67.00%)
Restricted Stock Units (RSUs) | Maximum
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected volatility 63.00% 74.00%
Expected dividend yield 3.10% 2.50%
Correlation of movement of total shareholder return maximum range 95.00% 94.00%