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Investments (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Investments $ 443us-gaap_LongTermInvestments $ 393us-gaap_LongTermInvestments  
Investments in equity affiliates      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Investments 295us-gaap_LongTermInvestments
/ us-gaap_FairValueByMeasurementBasisAxis
= ppg_InvestmentsInAndAdvancesToAffiliatesMember		 245us-gaap_LongTermInvestments
/ us-gaap_FairValueByMeasurementBasisAxis
= ppg_InvestmentsInAndAdvancesToAffiliatesMember		  
Marketable equity securities - Trading (See Note 9) | Trading      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Investments 74us-gaap_LongTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= ppg_TradingSecuritiesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= ppg_MarketableSecuritiesMember		 70us-gaap_LongTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= ppg_TradingSecuritiesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= ppg_MarketableSecuritiesMember		  
Other      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Investments $ 74us-gaap_LongTermInvestments
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_OtherCreditDerivativesMember		 $ 78us-gaap_LongTermInvestments
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_OtherCreditDerivativesMember		  
R S Cogen L L C [Member]      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Percentage Of Ownership Interests     50.00%ppg_PercentageOfOwnershipInterests
/ us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis
= ppg_RSCogenLLCMember