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Reflects the allowance for credit losses assigned to unfunded commitments and standby letters of credit as of the balance sheet date.

No definition available.

Name:	ntrs_UnfundedCommitmentsAndStandbyLettersOfCreditAllowance
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- References

No definition available.

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteoffsNetAbstract
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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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The balance of financing receivables that were individually evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 310
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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
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- References

No definition available.

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmountAbstract
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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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-Publisher FASB
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Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
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Period Type:	instant

- References

No definition available.