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Stock Options And Awards (Summary Of PSA Activity) (Detail) (Performance Unit Awards [Member], USD $)
12 Months Ended
Dec. 31, 2012
Performance Unit Awards [Member]
 
Nonvested Share Activity [Line Items]  
Nonvested balance at December 31, 2011, Number of Performance Units   
Granted, Number of Performance Units 46,350
Vested, Number of Performance Units   
Forfeited, Number of Performance Units   
Nonvested balance at December 31, 2012, Number of Performance Units 46,350
Nonvested balance at December 31, 2011, Weighted Average Grant Date Fair Value Per Performance Unit   
Granted, Weighted Average Grant Date Fair Value Per Performance Unit $ 84.66
Vested, Weighted Average Grant Date Fair Value Per Performance Unit   
Forfeited, Weighted Average Grant Date Fair Value Per Performance Unit   
Nonvested balance at December 31, 2012, Weighted Average Grant Date Fair Value Per Performance Unit $ 84.66