XML 36 R81.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Goodwill and Acquired Client Relationships - Schedule of Changes in Goodwill (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013
Changes in goodwill |  |
Balance at the beginning of the period | $ 2,341.7 us-gaap_Goodwill | $ 2,355.2 us-gaap_Goodwill
Goodwill acquired | 344.5 us-gaap_GoodwillAcquiredDuringPeriod | 0 us-gaap_GoodwillAcquiredDuringPeriod
Foreign currency translation | (33.4)us-gaap_GoodwillTranslationAdjustments | (13.5)us-gaap_GoodwillTranslationAdjustments
Balance at the end of the period | 2,652.8 us-gaap_Goodwill | 2,341.7 us-gaap_Goodwill
Institutional |  |
Changes in goodwill |  |
Balance at the beginning of the period | 1,076.3 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember | 1,078.5 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember
Goodwill acquired | 97.2 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember | 0 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember
Foreign currency translation | (14.4)us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember | (2.2)us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember
Balance at the end of the period | 1,159.1 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember | 1,076.3 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_InstitutionalMember
Mutual Fund |  |
Changes in goodwill |  |
Balance at the beginning of the period | 928.1 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember | 939.5 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember
Goodwill acquired | 208.1 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember | 0 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember
Foreign currency translation | (10.9)us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember | (11.4)us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember
Balance at the end of the period | 1,125.3 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember | 928.1 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_MutualFundMember
High Net Worth |  |
Changes in goodwill |  |
Balance at the beginning of the period | 337.3 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember | 337.2 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember
Goodwill acquired | 39.2 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember | 0 us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember
Foreign currency translation | (8.1)us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember | 0.1 us-gaap_GoodwillTranslationAdjustments / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember
Balance at the end of the period | $ 368.4 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember | $ 337.3 us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = amg_HighNetWorthMember

X
- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_GoodwillRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillTranslationAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=amg_HighNetWorthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=amg_InstitutionalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=amg_MutualFundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |