XML 77 R64.htm IDEA: XBRL DOCUMENT
v3.21.2

Goodwill and Acquired Client Relationships - Additional Information (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Jun. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Acquired Client Relationships |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible impairments |  | $ 14,000,000 |  | $ 0 |  |
Average projected growth rate |  | (14.00%) |  |  |  |
Discount rate for assets based fees |  | 15.00% |  |  |  |
Market participant tax rate |  | 25.00% |  |  |  |
Closure of Certain Retail Investment Products | Acquired Client Relationships |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible impairments |  | $ 10,900,000 |  |  |  |
Indefinite-lived acquired client relationships | $ 0 |  |  | 0 |  |
Controlling Interest | Acquired Client Relationships |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible impairments |  | 12,500,000 |  |  |  |
Controlling Interest | Closure of Certain Retail Investment Products | Acquired Client Relationships |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible impairments |  | 7,400,000 |  |  |  |
Acquired Client Relationships |  |  |  |  |  |
Intangible Assets |  |  |  |  |  |
Amortization and impairment expenses of intangible assets |  |  |  | 25,300,000 |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Finite-lived intangible, future amortization expense, remainder of fiscal year | 9,000,000 |  |  | 9,000,000 |  |
Finite-lived intangible, future amortization expense in year one | 30,000,000 |  |  | 30,000,000 |  |
Finite-lived intangible, future amortization expense in year two | 30,000,000 |  |  | 30,000,000 |  |
Finite-lived intangible, future amortization expense in year three | 15,000,000 |  |  | 15,000,000 |  |
Finite-lived intangible, future amortization expense in year four | 10,000,000 |  |  | 10,000,000 |  |
Finite-lived intangible, future amortization expense in year five | 10,000,000 |  |  | 10,000,000 |  |
Intangible impairments |  |  | $ 60,300,000 | 0 |  |
Indefinite-lived acquired client relationships | 903,800,000 |  | 0 | 903,800,000 |  | $ 909,000,000.0
Acquired Client Relationships | Controlling Interest |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible impairments |  |  | $ 32,800,000 |  |  |
Acquired Client Relationships | Intangible amortization and impairments |  |  |  |  |  |
Intangible Assets |  |  |  |  |  |
Amortization and impairment expenses of intangible assets | $ 8,900,000 | $ 7,000,000 |  | $ 25,300,000 | $ 48,200,000 |

X
- Definition Fair Value Assumptions, Average Projected Growth Rate + References No definition available. + Details
Name: | amg_FairValueAssumptionsAverageProjectedGrowthRate
Namespace Prefix: | amg_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value Assumptions, Discount Rate For Assets Based Fees + References No definition available. + Details
Name: | amg_FairValueAssumptionsDiscountRateForAssetsBasedFees
Namespace Prefix: | amg_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value Assumptions, Market Participant Tax Rate + References No definition available. + Details
Name: | amg_FairValueAssumptionsMarketParticipantTaxRate
Namespace Prefix: | amg_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | amg_IntangibleAssetLineItems
Namespace Prefix: | amg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 + Details
Name: | us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in remainder of current fiscal year. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
Name: | us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=amg_ClosureOfCertainRetailInvestmentProductsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=amg_IntangibleAmortizationandImpairmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |