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Marketable Securities (Details 1) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Contractual maturities of marketable securities    
Due in 1 year or less, amortized cost $ 61us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost  
Due in 1-5 years, amortized cost 28us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost  
Marketable securities, amortized cost 89us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis 154us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Due in 1 year or less, fair value 61us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue  
Due in 1-5 years, fair value 28us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue  
Marketable securities, fair value $ 89usg_AvailableForSaleDebtSecuritiesFairValue $ 154usg_AvailableForSaleDebtSecuritiesFairValue