Securities - Pledged assets (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Transfers and Servicing [Abstract]
Pledged assets	$ 101,000,000,000	$ 99,000,000,000
Pledged collateral for potential borrowings at the Federal Reserve Discount Window	84,000,000,000	74,000,000,000
Pledged securities	88,000,000,000	90,000,000,000
Pledged loans	8,000,000,000	6,000,000,000
Pledged interest-bearing deposits	2,000,000,000	1,000,000,000
Pledged trading assets	3,000,000,000	2,000,000,000
Pledged assets permitted to be sold or repledged	7,000,000,000	9,000,000,000
Market value of securities that can be sold or repledged	52,000,000,000	47,000,000,000
Fair value of securities received as collateral that have been resold or repledged	17,000,000,000	19,000,000,000
Cash segregated under other regulations	4,000,000,000	6,000,000,000
Securities segregated under other regulations	$ 1,000,000,000	$ 0

Assets pledged primarily for potential borrowing at the Fed discount window-other assets.

No definition available.

Name:	bk_PledgedAssetsNotSeparatelyReportedOtherAssetsPledgedAsCollateral
Namespace Prefix:	bk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Pledged Assets, Other, Not Separately Reported on Statement of Financial Position, Potential Borrowings at the Federal Reserve Discount Window

+ References

No definition available.

+ Details

Name:	bk_PledgedAssetsOtherNotSeparatelyReportedonStatementofFinancialPositionPotentialBorrowingsattheFederalReserveDiscountWindow
Namespace Prefix:	bk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Pledged Financial Instruments, Not Separately Reported, Trade Assets Pledged as Collateral

+ References

No definition available.

+ Details

Name:	bk_PledgedFinancialInstrumentsNotSeparatelyReportedTradeAssetsPledgedasCollateral
Namespace Prefix:	bk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to regulations other than SEC Regulations and the Commodity Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 305
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792

+ Details

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

- Definition

Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it is permitted by contract or custom to sell or re-pledge to counterparties as collateral.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

+ References

+ Details

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

- Definition

Fair value of the collateral, or portion thereof, that has been re-pledged, delivered, or otherwise used.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

The carrying amount, as of the date of the latest financial statement presented, of all assets that are pledged as collateral for the payment of the related debt obligation primarily arising from secured borrowings, repurchase agreements or other current or potential obligations, where the secured party does not have the right by contract or custom to sell or re-pledge the collateral and therefore are not reclassified and separately reported in the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

Fair value of securities deposited in a special reserve account for the exclusive benefit of customers pursuant to regulations other than SEC Regulations and the Commodity Exchange Act.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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