Goodwill and Other Intangible Assets - Summary of the Key Characteristics, Inputs, and Economic Assumptions Used to Estimate the Fair Value of the Company's MSRs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Servicing Asset at Fair Value, Amount	$ 1,181us-gaap_ServicingAssetAtFairValueAmount		$ 1,206us-gaap_ServicingAssetAtFairValueAmount
Mortgage Servicing Rights, Fair Value [Member]
Prepayment rate assumption (annual)	11.00%	11.00%
Decline in fair value from 10% adverse change	46		46
Decline in fair value from 20% adverse change	89		88
Discount rate (annual)	9.00%	10.00%
Decline in fair value from 10% adverse change	51		55
Decline in fair value from 20% adverse change	98		105
Weighted-average life (in years)	6 years 1 month	6 years 5 months
Weighted-average coupon	4.20%	4.20%
Mortgage Servicing Rights, Fair Value [Member]
Servicing Asset at Fair Value, Amount	$ 1,181	1,251	$ 1,206	$ 1,300

Goodwill and Other Intangible Assets - Summary of the Key Characteristics, Inputs, and Economic Assumptions Used to Estimate the Fair Value of the Company's MSRs (Detail) (USD $)
In Millions, unless otherwise specified

3 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Servicing Asset at Fair Value, Amount

$ 1,181us-gaap_ServicingAssetAtFairValueAmount

$ 1,206us-gaap_ServicingAssetAtFairValueAmount

Mortgage Servicing Rights, Fair Value [Member]

Prepayment rate assumption (annual)

11.00%us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesPrepaymentSpeed
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

Decline in fair value from 10% adverse change

46us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInPrepaymentSpeed
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= sti_MortgageServicingRightsFairValueMember

Decline in fair value from 20% adverse change

89us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

88us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed
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= sti_MortgageServicingRightsFairValueMember

Discount rate (annual)

9.00%us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

10.00%us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

Decline in fair value from 10% adverse change

51us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

55us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
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= sti_MortgageServicingRightsFairValueMember

Decline in fair value from 20% adverse change

98us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInDiscountRate
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

105us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInDiscountRate
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

Weighted-average life (in years)

6 years 1 month

6 years 5 months

Weighted-average coupon

4.20%sti_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesWeightedAverageCoupon
/ us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfAdverseChangeInAssumptionByTypeOfFinancialInstrumentAxis
= sti_MortgageServicingRightsFairValueMember

Mortgage Servicing Rights, Fair Value [Member]

Servicing Asset at Fair Value, Amount

$ 1,181us-gaap_ServicingAssetAtFairValueAmount
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= sti_MortgageServicingRightsFairValueMember

1,251us-gaap_ServicingAssetAtFairValueAmount
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= sti_MortgageServicingRightsFairValueMember

$ 1,206us-gaap_ServicingAssetAtFairValueAmount
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= sti_MortgageServicingRightsFairValueMember

$ 1,300us-gaap_ServicingAssetAtFairValueAmount
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= sti_MortgageServicingRightsFairValueMember

- Definition

Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Weighted Average Coupon

+ References

No definition available.

+ Details

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- Definition

Weighted average life of securitized assets regardless of when the transfer occurred, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)(2)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred.

+ References

+ Details

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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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Namespace Prefix:	us-gaap_
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- Definition

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122625-111746

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