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Segment Breakdown of Goodwill (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Mar. 31, 2014
Segment Reporting Information [Line Items]    
Goodwill $ 132,515us-gaap_Goodwill $ 132,515us-gaap_Goodwill
Cement [Member]    
Segment Reporting Information [Line Items]    
Goodwill 8,359us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_CementMember		 8,359us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_CementMember
Gypsum Wallboard [Member]    
Segment Reporting Information [Line Items]    
Goodwill 116,618us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_GypsumWallboardMember		 116,618us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_GypsumWallboardMember
Paperboard [Member]    
Segment Reporting Information [Line Items]    
Goodwill $ 7,538us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_PaperboardMember		 $ 7,538us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= exp_PaperboardMember