Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payments (Details)

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Share-Based Payments (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Employee Stock Options [Member]
Jun. 30, 2010
Employee Stock Options [Member]
Jun. 30, 2011
Employee Stock Options [Member]
Jun. 30, 2010
Employee Stock Options [Member]
Jun. 30, 2011
Key Employee Performance Share Based Plan[Member]
Jun. 30, 2011
Key Employee Performance Share Based Plan[Member]
Jun. 30, 2011
Key Employees Nonvested Shares Granted [Member]
Mar. 31, 2011
Key Employees Nonvested Shares Granted [Member]
Jun. 30, 2011
Key Employees Nonvested Shares Granted [Member]
Jun. 30, 2011
Nonemployee Director Nonvested Shares Granted Member
Jun. 30, 2010
Nonemployee Director Nonvested Shares Granted Member
Jun. 30, 2011
Nonemployee Director Nonvested Shares Granted Member
Jun. 30, 2010
Nonemployee Director Nonvested Shares Granted Member
Jun. 30, 2011
Non-employee Director Stock Options [Member]
Jun. 30, 2011
Employee Stock Purchase Plan 2005 [Member]
Jun. 30, 2011
Employee Stock Purchase Plan 2005 [Member]
Jun. 30, 2010
Employee Stock Purchase Plan 2005 [Member]
Employee activity - stock options [Abstract]                                          
Stock option grants expire (in years)         7                                
Stock option grants, vesting period (in years)         3                                
Weighted-average fair value of options (dollars per share)             $ 10.68 $ 8.24                          
Anniversary of the grant date of performance shares (in years)                 3                        
Number of years performance measured (in years)                 3                        
Median number of performance shares available for issuance (in shares)                 38,000                        
Performance share price performance, minimum (in hundredths)                 30.00%                        
Incremental number of issuable performance shares if Company share price outperforms peer group (in shares)                 75,000                        
Minimum percentage of peer group (in hundredths)                 90.00%                        
Risk free rate of return assumed in fair value calculation (in hundredths)                 1.40%                        
Fair value of the performance shares (dollars per share)                 $ 30.17                        
Expected stock price volatility         44.90% 45.70%                              
Expected dividend yield (in hundredths)         1.00% 1.30%                              
Weighted Average Risk- Free Interest Rate (in hundredths)                 1.40%                        
Expected life of options (in years)         4.6 4.5                              
Options [Abstract]                                          
Outstanding, beginning of period (in shares)         3,616,000   3,702,000                            
Granted (in shares)         0   118,000                            
Exercised (in shares)         (116,000)   (317,000)                            
Forfeited (in shares)         (2,000)   (5,000)                            
Outstanding, end of period (in shares)         3,498,000   3,498,000                     52,000      
Exercisable, end of period (in shares)         2,718,000   2,718,000                            
Outstanding, beginning of period (in dollars per share)         $ 26.00   $ 26.00                            
Shares Granted (in dollars per share)         $ 0.00   $ 29.00                            
Shares Excercised (in dollars per share)         $ 24.00   $ 23.00                     $ 21.00      
Forfeited (in dollars per share)         $ 29.00   $ 25.00                            
Outstanding, end of period (in dollars per share)         $ 26.00   $ 26.00                            
Exercisable, end of period (in dollars per share)         $ 27.00   $ 27.00                            
Aggregate Intrinsic Value Outstanding, end of period         $ 22,871   $ 22,871                            
Aggregate Intrinsic Value Exercisable, end of period         15,692   15,692                            
Weighted-average remaining contractual term Outstanding, end of period (in years)         3.9   3.9                     2.5      
Weighted-average remaining contractual term Exercisable, end of period (in years)         3.4   3.4                            
Non-vested employee share activity [Abstract]                                          
Non-vested shares granted to key employees (in shares)                       108                  
Weighted-average fair value of non-vested shares granted to key employees (in dollars per share)                       $ 28.61                  
2005 Employee Stock Purchase Plan (the ESPP) [Abstract]                                          
Shares authorized under employee stock purchase plan (in shares)                                     434,000 434,000  
Percentage of share price for shares issued under the ESPP (in hundredths)                                     90.00%    
Shares purchased by participants under the ESPP (in shares)                                       5,000 4,000
Weighted average price of shares purchased (dollars per share)                                     $ 25.82 $ 25.82 $ 22.98
Weighted-average fair value of each purchase right under the ESPP granted (dollars per share)                                       $ 7.97 $ 4.27
Additional Disclosures For Share Based Compensation [Abstract]                                          
Description of vesting period of non-employee directors                           1   1          
Weighted average risk-free interest rate (in hundredths)         2.40% 2.50% 2.40% 2.50%                          
Volatility Rate                 47.70%                        
Tax benefit related to share-based expense         252 372 556 862     100   154 72 57 126 113        
Share-based compensation expense 1,512 1,618 2,955 3,381 952 1,459 2,064 3,083 94 145 252   388 180 142 318 281     40 17
Unrecognized compensation cost         $ 4,727   $ 4,727   $ 988 $ 988 $ 2,601   $ 2,601 $ 660   $ 660          
Non-employee Director Activity - Options [Abstract]                                          
Terms of options granted to non-employee directors (in years) 10   10