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Rollforward of Credit Losses Recognized in Earnings Related to Securities (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]      
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities $ 0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNetAvailableforsaleSecurities $ 0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNetAvailableforsaleSecurities  
Available-for-sale Securities 26,761us-gaap_AvailableForSaleSecurities [1]   26,770us-gaap_AvailableForSaleSecurities [1]
Ending balance 25us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld 25us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld  
Mortgage-backed Securities, Issued by Private Enterprises [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale Securities 119us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		   123us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Other Than Temporarily Impaired Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale Securities $ 0us-gaap_AvailableForSaleSecurities
/ us-gaap_InvestmentTypeAxis
= sti_OtherThanTemporarilyImpairedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 $ 0us-gaap_AvailableForSaleSecurities
/ us-gaap_InvestmentTypeAxis
= sti_OtherThanTemporarilyImpairedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
[1] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $0 million and $369 million at March 31, 2015 and December 31, 2014, respectively.