XML 16 R55.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Affiliate Equity - Summary of Affiliate Equity Compensation (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013
Affiliate Equity [Abstract] |  |  |  |
Affiliate equity expense | $ 14.1 | $ 7.9 | $ 60.0 | $ 31.6
Tax benefit | $ 2.4 | $ 2.2 | $ 9.6 | $ 7.8

X
- Details
Name: | amg_AffiliateEquityAbstract
Namespace Prefix: | amg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Affiliate Equity Compensation, Tax Benefit from Compensation Expense + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationTaxBenefitfromCompensationExpense
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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