Annual report pursuant to Section 13 and 15(d)

Summary of Changes in Nonvested Stock and Weighted-Average Grant Date Fair Value (Detail)

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Summary of Changes in Nonvested Stock and Weighted-Average Grant Date Fair Value (Detail) (Nonvested Stock, USD $)
In Thousands, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Nonvested Stock
     
Shares      
Nonvested at the beginning of the year 1,431 1,310 1,110
Granted 685 513 553
Vested (440) (340) (317)
Forfeited (60) (52) (36)
Nonvested at the ending of the year 1,616 1,431 1,310
Weighted-Average Grant Date Fair Value      
Nonvested at the beginning of the year $ 31.79 $ 31.54 $ 33.10
Granted $ 44.59 $ 34.07 $ 33.27
Vested $ 29.02 $ 34.34 $ 38.08
Forfeited $ 33.31 $ 30.70 $ 33.20
Nonvested at the ending of the year $ 37.95 $ 31.79 $ 31.54