XML 60 R48.htm IDEA: XBRL DOCUMENT v3.23.1

Fair Value Measurements - Changes in Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Contingent Payment Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 21.0	$ 40.3
Purchases and issuances	0.0	0.0
Settlements and reductions	0.0	0.0
Net realized and unrealized (gains) losses	1.9	(8.9)
Balance, end of period	22.9	31.4
Net change in unrealized gains relating to instruments still held at the reporting date	1.9	(8.9)
Affiliate equity purchase obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	24.5	12.6
Purchases and issuances	44.2	40.6
Settlements and reductions	(7.5)	(5.3)
Net realized and unrealized (gains) losses	(0.3)	(0.3)
Balance, end of period	60.9	47.6
Net change in unrealized gains relating to instruments still held at the reporting date	$ (0.3)	$ (0.3)

X

- Definition

Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included In Earnings And Other Comprehensive Income (Loss)

+ References

No definition available.

+ Details

Name:	amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss
Namespace Prefix:	amg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Purchases And Issuances

+ References

No definition available.

+ Details

Name:	amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchasesAndIssuances
Namespace Prefix:	amg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements And Reductions

+ References

No definition available.

+ Details

Name:	amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlementsAndReductions
Namespace Prefix:	amg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of unrealized gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3) and still held.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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

X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

X

- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=amg_ContingentPaymentArrangementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=amg_ObligationsToRelatedPartiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: