Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Additional Information (Detail)

v2.4.0.8
Share-Based Compensation - Additional Information (Detail) (USD $)
12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2012
Plans
Dec. 31, 2011
Dec. 31, 2010
Mar. 31, 2008
Chairman and Chief Executive Officer [Member]
Dec. 31, 2012
Incentive Plan Stock Units Other [Member]
Dec. 31, 2012
Incentive Plan Stock Units [Member]
Dec. 31, 2012
Incentive Plan Stock Units [Member]
Incentive Plan Stock Units Other [Member]
Dec. 31, 2012
SARs [Member]
Dec. 31, 2012
SARs [Member]
Incentive Plan Stock Units Other [Member]
Dec. 31, 2012
Stock options [Member]
Mar. 31, 2008
Stock units [Member]
Chairman and Chief Executive Officer [Member]
Dec. 31, 2012
Stock units [Member]
Independent Director [Member]
Mar. 31, 2008
Market Condition 1 [Member]
Mar. 31, 2008
Market Condition Target 2 [Member]
Dec. 31, 2012
Market condition awards [Member]
Dec. 31, 2011
Market condition awards [Member]
Dec. 31, 2010
Market condition awards [Member]
Dec. 31, 2012
Service condition awards [Member]
Dec. 31, 2011
Service condition awards [Member]
Dec. 31, 2010
Service condition awards [Member]
Dec. 31, 2012
Market and performance condition awards [Member]
Dec. 31, 2011
Market and performance condition awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                            
Number of share based compensation plan 5                                          
Common shares authorized under 2005 Stock Incentive Plan 14,400,000                                          
Common shares remain for future issuance under share based compensation plans 3,100,000                                          
Contractual term           3 years   10 years   10 years                        
Vesting period beginning from the grant date         5 years   3 years 5 years 3 years 5 years 4 years                      
Stock units vesting rate                       25.00%                    
Stock units vesting rate during first three years                     30.00%                      
Stock units vesting rate during fourth year                     10.00%                      
Granted stock unit awards to Chairman and Chief Executive Officer vesting       Over a four-year period at a rate of 30% during each of the first three years and 10% during the fourth year                                    
Stock price appreciation rate                         10.00% 15.00%                
Share-based compensation expense                             $ 700,000 $ 2,900,000 $ 3,000,000 $ 22,700,000 $ 19,200,000 $ 20,000,000 $ 4,600,000 $ 1,400,000
Realized income tax benefit for all awards 9,500,000 7,500,000 7,400,000                                      
Unrecognized compensation cost on non-vested stock awards                                   41,200,000     9,000,000  
Unrecognized compensation cost on non-vested stock awards, weighted-average period of recognition                                   1 year 4 months 24 days     2 years  
Excess tax benefit 29,684,000 26,241,000 9,254,000                                      
Total intrinsic value of awards exercised for options and SARs 98,600,000 133,800,000 63,800,000                                      
Weighted-average grant date fair value of SARs granted                                    $ 15.36 $ 21.23 $ 9.32   $ 17.37
Total vesting date fair value of stock units $ 24,300,000 $ 19,800,000 $ 10,300,000                                      
Percent of fair market value for which eligible employees can purchase common shares under employee stock purchase plan 85.00%                                          
Reserved for issuance under employee stock purchase plan 2,000,000                                          
Future Issuance of employee stock purchase plan 1,800,000