Loans and Allowance for Credit Losses - Amortized Cost Basis (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	$ 7,047		$ 8,336
Financing receivable, originated, year two	5,325		794
Financing receivable, originated, year three	683		2,012
Financing receivable, originated, year four	1,987		1,457
Financing receivable, originated, year five	1,384		810
Financing receivable, originated more than five years before current fiscal year	990		263
Revolving Loans	17,668		18,852
Loans, gross, excluding loans classified as held-for-sale	35,084		32,524
Interest income	70	$ 86
Financing receivable, held-for-sale	57		8
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	29,339		27,196
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	5,287		4,984
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	291		180
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	167		164
Commercial and Financial Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	32,526		29,970
Commercial and Financial Segment \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	27,112		24,974
Commercial and Financial Segment \| Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	5,018		4,714
Commercial and Financial Segment \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	229		118
Commercial and Financial Segment \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	167		164
Commercial and Financial Segment \| Geographic Distribution, Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	3,209		3,084
Financing receivable, originated, year two	1,360		415
Financing receivable, originated, year three	404		1,194
Financing receivable, originated, year four	1,173		512
Financing receivable, originated, year five	471		414
Financing receivable, originated more than five years before current fiscal year	388		7
Revolving Loans	12,935		13,934
Loans, gross, excluding loans classified as held-for-sale	19,940		19,560
Commercial and Financial Segment \| Geographic Distribution, Domestic \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	3,135		1,988
Financing receivable, originated, year two	276		59
Financing receivable, originated, year three	59		347
Financing receivable, originated, year four	347		2
Financing receivable, originated, year five	2		37
Financing receivable, originated more than five years before current fiscal year	35		0
Revolving Loans	12,326		13,591
Loans, gross, excluding loans classified as held-for-sale	16,180		16,024
Commercial and Financial Segment \| Geographic Distribution, Domestic \| Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	74		1,096
Financing receivable, originated, year two	1,064		351
Financing receivable, originated, year three	341		706
Financing receivable, originated, year four	660		425
Financing receivable, originated, year five	395		350
Financing receivable, originated more than five years before current fiscal year	325		7
Revolving Loans	609		343
Loans, gross, excluding loans classified as held-for-sale	3,468		3,278
Commercial and Financial Segment \| Geographic Distribution, Domestic \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	0		0
Financing receivable, originated, year two	20		0
Financing receivable, originated, year three	0		70
Financing receivable, originated, year four	96		29
Financing receivable, originated, year five	29		19
Financing receivable, originated more than five years before current fiscal year	19		0
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	164		118
Commercial and Financial Segment \| Geographic Distribution, Domestic \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	0		0
Financing receivable, originated, year two	0		5
Financing receivable, originated, year three	4		71
Financing receivable, originated, year four	70		56
Financing receivable, originated, year five	45		8
Financing receivable, originated more than five years before current fiscal year	9		0
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	128		140
Commercial and Financial Segment \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	3,804		4,648
Financing receivable, originated, year two	3,361		201
Financing receivable, originated, year three	130		264
Financing receivable, originated, year four	260		228
Financing receivable, originated, year five	197		120
Financing receivable, originated more than five years before current fiscal year	101		31
Revolving Loans	4,733		4,918
Loans, gross, excluding loans classified as held-for-sale	12,586		10,410
Commercial and Financial Segment \| Non-U.S. \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	3,436		4,087
Financing receivable, originated, year two	2,839		0
Financing receivable, originated, year three	0		0
Financing receivable, originated, year four	0		0
Financing receivable, originated, year five	0		0
Financing receivable, originated more than five years before current fiscal year	0		0
Revolving Loans	4,657		4,863
Loans, gross, excluding loans classified as held-for-sale	10,932		8,950
Commercial and Financial Segment \| Non-U.S. \| Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	362		561
Financing receivable, originated, year two	494		201
Financing receivable, originated, year three	130		264
Financing receivable, originated, year four	260		204
Financing receivable, originated, year five	158		120
Financing receivable, originated more than five years before current fiscal year	70		31
Revolving Loans	76		55
Loans, gross, excluding loans classified as held-for-sale	1,550		1,436
Commercial and Financial Segment \| Non-U.S. \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	6
Financing receivable, originated, year two	28
Financing receivable, originated, year three	0
Financing receivable, originated, year four	0
Financing receivable, originated, year five	0
Financing receivable, originated more than five years before current fiscal year	31
Revolving Loans	0
Loans, gross, excluding loans classified as held-for-sale	65
Commercial and Financial Segment \| Non-U.S. \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	0		0
Financing receivable, originated, year two	0		0
Financing receivable, originated, year three	0		0
Financing receivable, originated, year four	0		24
Financing receivable, originated, year five	39		0
Financing receivable, originated more than five years before current fiscal year	0		0
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	39		24
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	2,558		2,554
Commercial real estate \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	2,227		2,222
Commercial real estate \| Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	269		270
Commercial real estate \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	62		62
Commercial real estate \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	0		0
Commercial real estate \| Geographic Distribution, Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	34		604
Financing receivable, originated, year two	604		178
Financing receivable, originated, year three	149		554
Financing receivable, originated, year four	554		717
Financing receivable, originated, year five	716		276
Financing receivable, originated more than five years before current fiscal year	501		225
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	2,558		2,554
Commercial real estate \| Geographic Distribution, Domestic \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	34		580
Financing receivable, originated, year two	580		129
Financing receivable, originated, year three	100		383
Financing receivable, originated, year four	384		657
Financing receivable, originated, year five	656		276
Financing receivable, originated more than five years before current fiscal year	473		197
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	2,227		2,222
Commercial real estate \| Geographic Distribution, Domestic \| Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	0		24
Financing receivable, originated, year two	24		49
Financing receivable, originated, year three	49		149
Financing receivable, originated, year four	148		20
Financing receivable, originated, year five	20		0
Financing receivable, originated more than five years before current fiscal year	28		28
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	269		270
Commercial real estate \| Geographic Distribution, Domestic \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated, year one	0		0
Financing receivable, originated, year two	0		0
Financing receivable, originated, year three	0		22
Financing receivable, originated, year four	22		40
Financing receivable, originated, year five	40		0
Financing receivable, originated more than five years before current fiscal year	0		0
Revolving Loans	0		0
Loans, gross, excluding loans classified as held-for-sale	$ 62		$ 62

Financing Receivable, Excluding Accrued Interest, Before Allowance For Credit Loss, Excluding Held For Sale Receivables

No definition available.

Name:	stt_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossExcludingHeldForSaleReceivables
Namespace Prefix:	stt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount excluding accrued interest of financing receivable originated more than five years prior to current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable that can be withdrawn, repaid, and redrawn.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable originated four years prior to current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable originated three years prior to current fiscal year.

+ References

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable originated in current fiscal year.

+ References

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable originated two years prior to current fiscal year.

+ References

+ Details

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

- Definition

Amount excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, before valuation allowance, of financing receivable classified as held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124265262&loc=d3e48678-111004

+ Details

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

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_InternalInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=stt_SpeculativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=stt_CommercialandFinancialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GeographicDistributionAxis=us-gaap_GeographicDistributionDomesticMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GeographicDistributionAxis=us-gaap_GeographicDistributionForeignMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: