Derivative instruments - Impact of Hedging Derivatives Used in Net Investment Hedging Relationships (Details) - FX contracts - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives	$ 437	$ (341)	$ (6)
Net interest revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) reclassified from accumulated OCI into income	$ 0	$ 0	$ 0

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.

No definition available.

+ Details

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

- Definition

Amount, before tax and reclassification, of gain (loss) from derivative designated and qualifying as net investment hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CCC
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998896-113959

+ Details

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

- Definition

Amount, before tax, of reclassification from accumulated other comprehensive income (AOCI) for gain (loss) from derivative designated and qualifying as net investment hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CCC
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998896-113959

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=bk_InterestIncomeExpenseNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: