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Weighted Average Asset Allocation for Pension Plans and Target Allocation (Detail)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 100.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations  
Actual Allocation 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Equity Securities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 58.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember		  
Equity Securities | United States    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 49.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= country_US		  
Actual Allocation 47.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= country_US		 48.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= country_US
Equity Securities | International    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 9.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= slgn_InternationalMember		  
Actual Allocation 10.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= slgn_InternationalMember		 10.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_StatementGeographicalAxis
= slgn_InternationalMember
Debt securities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 42.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember		  
Actual Allocation 42.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember		 41.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
Cash and cash equivalents    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 0.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_CashAndCashEquivalentsMember		  
Actual Allocation 1.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_CashAndCashEquivalentsMember		 1.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_InvestmentTypeAxis
= us-gaap_CashAndCashEquivalentsMember