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Stock-Based Compensation Plans Restricted Stock Units (Details) - Restricted stock units (RSUs) [Member] - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Restricted Stock Units [Abstract]      
Non-vested at beginning of year 47,708    
Granted 46,426    
Vested (21,018)    
Forfeited (10,415)    
Non-vested at end of year 62,701 47,708  
Weighted Average Grant Date Fair Value [Abstract]      
Non-vested at beginning of year $ 81.52    
Granted 57.11 $ 70.64 $ 98.24
Vested 84.37    
Forfeited 65.78    
Non-vested at end of year 65.35 81.52  
Weighted average grant date fair value granted during year $ 57.11 $ 70.64 $ 98.24
Total fair value of restricted stock units that vested during year $ 1.8 $ 4.2 $ 4.4