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v3.3.1.900

Forward Equity Sale Agreement (Details) | Dec. 31, 2015 USD ($)
--- | ---
Forward Equity Sale Agreements |
Derivative remaining notional amount | $ 250,000,000

X
- Definition Derivative, Remaining Notional Amount + References No definition available. + Details
Name: | amg_DerivativeRemainingNotionalAmount
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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