XML 74 R58.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2014
Income Tax Disclosure [Abstract] |
Decrease in deferred tax liability | $ 57.5
Reclassification of Deferred Tax Liability | 54.5
Liability for uncertain tax positions including interest and related charges | 19.9
Accrued income tax interest and related charges | 1.7
Unrecognized tax benefits that, if recognized, would affect effective tax rate | $ 16.9

X
- Definition Decrease in Deferred Tax Liability + References No definition available. + Details
Name: | amg_DecreaseinDeferredTaxLiability
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reclassification of Deferred Tax Liability + References No definition available. + Details
Name: | amg_ReclassificationofDeferredTaxLiability
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The gross amount of unrecognized tax benefits, including interest and related charges, pertaining to uncertain tax positions taken in tax returns as of the balance sheet date. + References No definition available. + Details
Name: | amg_UnrecognizedTaxBenefitsIncludingTaxInterestAndRelatedChargesAccrued
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant