Loans and asset quality - Credit Risk Indicators Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of exposure to investment grade securities	96.00%
Percentage of financial institution exposure secured	66.00%
Percent of financial institution exposure expiring within one year	82.00%
Loans	$ 75,195,000,000	$ 71,570,000,000
Reverse repurchase agreements, allowance for credit loss	$ 0	0
Wealth management mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan to value ratio at origination (percent)	61.00%
Loans	$ 8,707,000,000	8,950,000,000
Wealth management mortgages \| California \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	20.00%
Wealth management mortgages \| New York \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	14.00%
Wealth management mortgages \| Florida \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	11.00%
Wealth management mortgages \| Massachusetts \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	8.00%
Wealth management mortgages \| Other \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	47.00%
Total wealth management loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of past due mortgages (less than)	1.00%
Other residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 1,767,000,000	1,068,000,000
Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 23,084,000,000	19,137,000,000
Minimum collateral margin	1
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 2,700,000,000
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 2,652,000,000	$ 3,519,000,000
Overdraft repayment period	2 days	2 days

Financing Receivable, Minimum Collateral Margin

No definition available.

Name:	bk_FinancingReceivableMinimumCollateralMargin
Namespace Prefix:	bk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Loan To Value Ratio

+ References

No definition available.

+ Details

Name:	bk_LoanToValueRatio
Namespace Prefix:	bk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Overdraft Repayment Period

+ References

No definition available.

+ Details

Name:	bk_OverdraftRepaymentPeriod
Namespace Prefix:	bk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Financial Institution Exposure To Investment Grade Securities

+ References

No definition available.

+ Details

Name:	bk_PercentageOfFinancialInstitutionExposureToInvestmentGradeSecurities
Namespace Prefix:	bk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of Financial Institution Exposure Secured

+ References

No definition available.

+ Details

Name:	bk_PercentageofFinancialInstitutionExposureSecured
Namespace Prefix:	bk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percent of Financial Institution Exposure Expiring Within One Year

+ References

No definition available.

+ Details

Name:	bk_PercentofFinancialInstitutionExposureExpiringWithinOneYear
Namespace Prefix:	bk_
Data Type:	dtr-types: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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

+ Details

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

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

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

- Definition

Percentage of financing receivable balance that is past due.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivablePercentPastDue1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of allowance for credit loss on security purchased under agreement to resell.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bk_WealthManagementMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GeographicConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_NY
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_FL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_MA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=bk_OtherStatesNotSeparatelyDisclosedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bk_WealthManagementLoansAndMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bk_OtherResidentialMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bk_MarginLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bk_OverdraftsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_BankOverdraftsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: