v2.4.0.8
Retirement Plans Retirement Plans - Additional Information (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
401(k) Plan
     
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Defined contribution plan expense $ 5.4 $ 5.3 $ 4.8
Nonqualified Deferred Compensation Plan
     
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Defined contribution plan expense 0.9 0.8 0.7
Percentage of eligible employee contribution matched by employer 50.00%    
Maximum percentage of employee deferrals subject to match by employer 6.00%    
Period after which a participant may receive amounts deferred 5 years    
Vesting period of matching contributions 4 years    
Deferred compensation liabilities 19.8 14.1  
Number of life settlement contracts 184 184  
Face value of life settlement contracts 81.8 80.6  
Cash surrender value of life insurance policies $ 19.5 $ 13.4