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Marketable Securities (Details 1) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Amortized Cost    
Due in 1 year or less $ 96us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost  
Due in 1-5 years 58us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost  
Total marketable securities 154us-gaap_AvailableForSaleSecuritiesAmortizedCost  
Fair Value    
Due in 1 year or less 96us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue  
Due in 1-5 years 58us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue  
Total marketable securities $ 154usg_AvailableForSaleDebtSecuritiesFairValue $ 142usg_AvailableForSaleDebtSecuritiesFairValue