XML 13 R48.htm IDEA: XBRL DOCUMENT v2.4.0.6
Stock Repurchase Program - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2013
Dec. 31, 2011
Stock Repurchase Program [Line Items]    
Common stock repurchase authorized amount   $ 150.0
Common stock repurchased, shares 121,263  
Common stock repurchased, value 5.1  
Common stock repurchase price per share $ 42.47  
Common stock repurchase authorization amount available 100.7  
Common stock repurchased and retired, shares 41,263  
Common stock repurchased and retired, value $ 1.8