Stock Incentive Plans (Details) (USD $)
0 Months Ended 12 Months Ended
May 19, 2010
Dec. 31, 2014
Dec. 31, 2013
Feb. 03, 2015
Stock Incentive Plans        
Maximum number of shares that may be delivered to participants   4,000,000    
Period from effective date after which no awards may be granted 10 years      
Stock Incentive Plans        
Treasury Stock, Shares   1,426,323 1,482,777  
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased   895,655    
Maximum | Options and SARs        
Stock Incentive Plans        
Shares available for grant during any calendar year   400,000    
Maximum | Stock awards        
Stock Incentive Plans        
Shares available for grant during any calendar year   200,000    
Maximum | Cash incentive awards and cash-settled stock awards        
Stock Incentive Plans        
Amount of award payable with respect to any calendar year   1,000,000    
Subsequent event        
Stock Incentive Plans        
Shares authorized for repurchase under stock repurchase plan       2,000,000