XML 88 R69.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Commitments and Contingencies (Details) | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) claim
Commitments and Contingencies |  |
Co-investment commitments in partnership |  | $ 92,200,000
Prior Owner |  |
Commitments and Contingencies |  |
Reimbursable amount of investment commitments |  | 11,800,000
Affiliate Partners |  |
Commitments and Contingencies |  |
Acquisition agreements contingency liability |  | 84,900,000
Contingent payment obligations |  | 10,300,000
Affiliate Partners | Scenario, Forecast |  |
Commitments and Contingencies |  |
Contingent payment obligations | $ 3,000,000 |
Equity Method Investee |  |
Commitments and Contingencies |  |
Acquisition agreements contingency liability |  | 312,000,000
Contingent payment obligations |  | $ 0
Third Avenue Focused Credit Fund | Affiliate Partners |  |
Commitments and Contingencies |  |
Number of actions pending | claim |  | 1
Loss contingency reserve |  | $ 15,000,000

X
- Definition For contingent consideration arrangements recognized in connection with a business combination, this element represents the expected payment amounts during the period. + References No definition available. + Details
Name: | amg_BusinessCombinationContingentConsiderationArrangementsExpectedPayments
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition The amount that the entity agreed to co-invest in certain investment partnerships where the entity serves as the general partner. + References No definition available. + Details
Name: | amg_InvestmentCommitmentAmount
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the contractual obligation to reimburse the entity for co-investments in investment partnerships. + References No definition available. + Details
Name: | amg_ReimbursableAmountOfInvestmentCommitments
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of pending claims pertaining to a loss contingency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 + Details
Name: | us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=amg_PriorOwnerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_AffiliatedEntityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_EquityMethodInvesteeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LitigationCaseAxis=amg_ThirdAvenueFocusedCreditFundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |