XML 13 R54.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Affiliate Equity (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 | Dec. 31, 2013
Affiliate Equity [Abstract] |  |  |  |  |
Compensation expenses related to affiliate equity noncontrolling interests | $ 7.9 | $ 2.2 | $ 35.1 | $ 11.3 |
Affiliate equity compensation cost not yet recognized | 76.1 |  | 76.1 |  | 68.2
Affiliate equity compensation cost not yet recognized attributable to noncontrolling interest | $ 43.2 |  | $ 43.2 |  | $ 32.1
Period for recognition |  |  | 4 years |  |

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

X
- Definition Affiliate Equity, Compensation Cost Not yet Recognized + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationCostNotyetRecognized
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Affiliate Equity, Compensation Cost Not yet Recognized Attributable to Noncontrolling Interest + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationCostNotyetRecognizedAttributabletoNoncontrollingInterest
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Affiliate Equity, Compensation Cost Not yet Recognized, Period for Recognition + References No definition available. + Details
Name: | amg_AffiliateEquityCompensationCostNotyetRecognizedPeriodforRecognition
Namespace Prefix: | amg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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