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Inventories
6 Months Ended
Oct. 31, 2012
Inventory Disclosure [Abstract]  
Inventories
 Inventories 
We use the last-in, first-out (“LIFO”) method to determine the cost of most of our inventories.  If the LIFO method had not been used, inventories at current cost would have been $213.0 million higher than reported as of April 30, 2012, and $215.3 million higher than reported as of October 31, 2012.  Changes in the LIFO valuation reserve for interim periods are based on a proportionate allocation of the estimated change for the entire fiscal year.