Debt Instrument, Covenant, Period Prior To Date Of Repayment

No definition available.

Name:	stt_DebtInstrumentCovenantPeriodPriorToDateOfRepayment
Namespace Prefix:	stt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Redemption Price, Gain (Loss) On Redemption

+ References

No definition available.

+ Details

Name:	stt_DebtInstrumentRedemptionPriceGainLossOnRedemption
Namespace Prefix:	stt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Redemption Price, Principal Amount Redeemed

+ References

No definition available.

+ Details

Name:	stt_DebtInstrumentRedemptionPricePrincipalAmountRedeemed
Namespace Prefix:	stt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of lessee's right to use underlying asset under finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_FinanceLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=stt_StateStreetBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stt_FloatingRateSubordinatedDebenturesDue2047Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stt_FloatingRateSubordinatedNotesDue2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stt_ReplacementCapitalCovenantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stt_TwoPointSixFivePercentNotesDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt - Narrative (Details) - USD ($)			3 Months Ended
Long-Term Debt - Narrative (Details) - USD ($)	Nov. 20, 2019	Nov. 19, 2019	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term finance leases			$ 78,000,000	$ 102,000,000
State Street Bank
Debt Instrument [Line Items]
Long-term finance leases			136,000,000	$ 190,000,000
Floating Rate Subordinated Debentures Due 2047 \| Junior subordinated debentures
Debt Instrument [Line Items]
Amount redeemed			297,000,000
Aggregate principal amount			800,000,000
Gain on redemption			44,000,000
Floating-rate subordinated notes due to State Street Capital Trust I in 2028 \| Junior subordinated debentures
Debt Instrument [Line Items]
Amount redeemed			50,000,000
Aggregate principal amount			$ 150,000,000
Replacement Capital Covenant
Debt Instrument [Line Items]
Amount redeemed	$ 50,000,000
Period prior to date of repayment		180 days
2.65% notes due 2026 \| Senior notes
Debt Instrument [Line Items]
Interest rate on debt			2.65%