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Fair Value Measurements - Schedule of Changes in Level 3 Financial Assets and Liabilities (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015
Contingent Payment Arrangements |  |  |
Changes in level 3 assets and liabilities |  |  |
Balance, beginning of period |  | $ 10.2 | $ 59.3
Net (gains) losses | [1] | (1.6) | (40.9)
Purchases and issuances |  | 0.0 | 9.3
Settlements and reductions |  | 0.0 | (17.5)
Balance, end of period |  | 8.6 | 10.2
Net change in unrealized (gains) losses relating to instruments still held at the reporting date |  | (1.6) | (40.9)
Obligations to Related Parties |  |  |
Changes in level 3 assets and liabilities |  |  |
Balance, beginning of period |  | 62.3 | 21.5
Net (gains) losses |  | 3.1 | (1.4)
Purchases and issuances |  | 69.1 | 158.0
Settlements and reductions |  | (122.4) | (115.8)
Balance, end of period |  | 12.1 | 62.3
Net change in unrealized (gains) losses relating to instruments still held at the reporting date |  | $ 0.0 | $ 0.0
[1] | Accretion and changes in the expected value of the Company’s contingent payment arrangements are recorded in Imputed interest expense and contingent payment arrangements.

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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
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- Definition Represents total realized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. + References No definition available. + Details
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- Definition Represents assets and liabilities measured at fair value using significant unobservable inputs (Level 3) which are required for reconciliation purposes of beginning and ending balances. + References No definition available. + Details
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- Definition Represents settlements and reductions which have taken place during the period in relation to assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3). + References No definition available. + Details
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Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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- Definition Represents total unrealized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. + References No definition available. + Details
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- Details
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- Details
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