Quarterly report pursuant to Section 13 or 15(d)

Stock Compensation Plans (Detail)

v2.4.0.6
Stock Compensation Plans (Detail) (USD $)
6 Months Ended
Jun. 30, 2012
Mar. 13, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Grant Date 2012-03-12  
Grant Date Market Price 63.62  
Average Expected Term (Years) 2 years 9 months 18 days  
Fair Value 77.78  
Expected Volatility 56.00%  
Risk-Free Interest Rate 0.45%  
Dividend Yield 3.93%  
Fair Value (Percent of Grant Date Market Price) 122.26%  
Ice Plan [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Performance shares granted 312,540  
Restricted shares granted 114,070  
Number of shares granted under the plan 426,610  
2010 to 2012 Performance Period [Member] | Lower Limit [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum payout ratio 0.00%  
2010 to 2012 Performance Period [Member] | Upper Limit [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Maximum payout ratio 150.00%  
2011 To 2013 And The 2012 to 2014 Performance Periods [Member] | Lower Limit [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum payout ratio 0.00%  
2011 To 2013 And The 2012 to 2014 Performance Periods [Member] | Upper Limit [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Maximum payout ratio 200.00%  
2012 Equity Plan [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares granted under the plan 11,425  
Maximum number of shares that may be issued   6,000,000