XML 99 R58.htm IDEA: XBRL DOCUMENT
v3.19.3

Fair Value Measurements - Quantitative Information used in Valuing Level 3 Liabilities (Details) - Discounted cash flow $ in Millions | Sep. 30, 2019 USD ($) | Dec. 31, 2018 USD ($)
--- | --- | ---
Contingent Payment Arrangements | Growth rates |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Contingent payment arrangements, measurement input |  |  | 0.07
Contingent Payment Arrangements | Growth rates | Weighted Average |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Contingent payment arrangements, measurement input | [1] |  | 0.07
Contingent Payment Arrangements | Discount rates |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Contingent payment arrangements, measurement input |  |  | 0.15
Contingent Payment Arrangements | Discount rates | Weighted Average |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Contingent payment arrangements, measurement input | [1] |  | 0.15
Affiliate Equity Repurchase Obligations | Growth rates | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input |  | (0.04) | (0.04)
Affiliate Equity Repurchase Obligations | Growth rates | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input |  | 0.09 | 0.09
Affiliate Equity Repurchase Obligations | Growth rates | Weighted Average |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input | [1] | 0.07 | 0.03
Affiliate Equity Repurchase Obligations | Discount rates | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input |  | 0.14 | 0.14
Affiliate Equity Repurchase Obligations | Discount rates | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input |  | 0.17 | 0.16
Affiliate Equity Repurchase Obligations | Discount rates | Weighted Average |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Affiliate equity repurchase obligations, measurement input | [1] | 0.15 | 0.15
Significant Unobservable Inputs (Level 3) | Contingent Payment Arrangements |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Fair Value |  | $ 0.0 | $ 1.9
Significant Unobservable Inputs (Level 3) | Affiliate Equity Repurchase Obligations |  |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |  |
Fair Value |  | $ 36.8 | $ 36.2
[1] | Calculated by comparing the relative fair value of an arrangement or obligation to its respective total.

X
- Definition Contingent Payment Arrangement, Measurement Input + References No definition available. + Details
Name: | amg_ContingentPaymentArrangementMeasurementInput
Namespace Prefix: | amg_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Obligations to Related Parties, Measurement Input + References No definition available. + Details
Name: | amg_ObligationstoRelatedPartiesMeasurementInput
Namespace Prefix: | amg_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of financial and nonfinancial obligations. + 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 (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=amg_DiscountedCashFlowValuationTechniqueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputLongTermRevenueGrowthRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
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: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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