Held To Maturity Securities, Transferred From Available For Sale

No definition available.

Name:	ntrs_HeldToMaturitySecuritiesTransferredFromAvailableForSale
Namespace Prefix:	ntrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Held To Maturity Securities, Transferred From Available For Sale, Unrealized Gain (Loss)

+ References

No definition available.

+ Details

Name:	ntrs_HeldToMaturitySecuritiesTransferredFromAvailableForSaleUnrealizedGainLoss
Namespace Prefix:	ntrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after tax, of adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 10B
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124260725&loc=SL120268667-111560

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
Subsequent Events (Details) - USD ($)	Jul. 26, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Subsequent Event [Line Items]
Held to maturity securities, transferred from available for sale		$ 0	$ 6,900,000,000	$ 0	$ 6,900,000,000
Subsequent Event
Subsequent Event [Line Items]
Held to maturity securities, transferred from available for sale	$ 6,380,000,000
Held to maturity securities, transferred from available for sale, unrealized loss	889,500,000
OCI, debt securities, available-for-sale, transfer to held-to-maturity, adjustment from AOCI for amortization of loss	$ 665,800,000