XML 118 R95.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Affiliate Equity - Recognized and Unrecognized Expense (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Affiliate Equity Expense |  |  |
Non-controlling interest | $ 36.8 | $ 31.2 | $ 51.6
Total | 50.0 | 41.2 | 68.5
Non- controlling Interests |  |  |
Affiliate Equity Expense |  |  |
Total | $ 36.8 | $ 31.2 | $ 51.6
Unrecognized Affiliate Equity Expense |  |  |
Remaining Life | 6 years | 5 years | 5 years
Non-Controlling Interest | $ 95.9 | $ 70.7 | $ 51.9
Controlling Interest |  |  |
Affiliate Equity Expense |  |  |
Controlling interest | 13.2 | 10.0 | 16.9
Unrecognized Affiliate Equity Expense |  |  |
Controlling Interest | $ 33.3 | $ 31.3 | $ 22.4
Remaining Life | 5 years | 4 years | 3 years

X
- Definition Affiliate Equity Compensation Expense, Attributable to Noncontrolling Interest + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationExpenseAttributabletoNoncontrollingInterest
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Affiliate Equity Compensation Expense, Including Portion Attributable to Noncontrolling Interest + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationExpenseIncludingPortionAttributabletoNoncontrollingInterest
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition [Line Items] for Affiliate Equity [Table] + References No definition available. + Details
Name: | amg_AffiliateEquityLineItems
Namespace Prefix: | amg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Affiliate Equity Unrecognized Compensation Expense, Attributable to Noncontrolling Interest + References No definition available. + Details
Name: | amg_AffiliateEquityUnrecognizedCompensationExpenseAttributabletoNoncontrollingInterest
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Affiliate Equity, Unrecognized Compensation Expense, Weighted Average Period of Recognition + References No definition available. + Details
Name: | amg_AffiliateEquityUnrecognizedCompensationExpenseWeightedAveragePeriodofRecognition
Namespace Prefix: | amg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the compensation expenses related to Affiliate equity. + References No definition available. + Details
Name: | amg_CompensationExpensesRelatedToAffiliateEquity
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Unrecognized Affiliate Equity Expense [Abstract] + References No definition available. + Details
Name: | amg_UnrecognizedAffiliateEquityExpenseAbstract
Namespace Prefix: | amg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Unrecognized Compensation Expenses Related to Affiliate Equity Attributable to Controlling Interest + References No definition available. + Details
Name: | amg_UnrecognizedCompensationExpensesRelatedtoAffiliateEquityAttributabletoControllingInterest
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_NoncontrollingInterestMember
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: |