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Stock Repurchase Program - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 6 Months Ended
Nov. 30, 2014
Nov. 30, 2014
Stock Repurchase Programs [Line Items]    
Authorization of stock repurchase program   Jan. 08, 2008
Shares repurchased 45,000rpm_RepurchaseOfCommonStockShares  
Shares repurchased, value $ 1.8rpm_RepurchaseOfCommonStockValue  
Minimum    
Stock Repurchase Programs [Line Items]    
Shares authorized to be repurchased, per year 1,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 1,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Maximum    
Stock Repurchase Programs [Line Items]    
Shares authorized to be repurchased, per year 2,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 2,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MaximumMember