XML 97 R64.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Fair Value Measurements (Details 3) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011
Other investments |  |
Changes in level 3 assets and liabilities |  |
Balance at the beginning of the period | $ 103.4 | $ 85.7
Net realized gains/losses | (3.2) | (0.2)
Net unrealized gains/losses relating to instruments still held at the reporting date | 11.0 | 9.6
Purchases and issuances | 18.8 | 17.7
Settlements and reductions | (11.1) | (9.4)
Balance at the end of period | 118.9 | 103.4
Contingent payment arrangements |  |
Changes in level 3 assets and liabilities |  |
Balance at the beginning of the period | 87.1 | 77.6
Net realized gains/losses | (0.6) |
Net unrealized gains/losses relating to instruments still held at the reporting date | (40.2) | 9.5
Purchases and issuances | 24.8 |
Settlements and reductions | (40.1) |
Balance at the end of period | 31.0 | 87.1
Obligations to related parties |  |
Changes in level 3 assets and liabilities |  |
Balance at the beginning of the period | 92.0 | 79.6
Net realized gains/losses | 1.0 | 0.4
Net unrealized gains/losses relating to instruments still held at the reporting date | 0.8 | 1.7
Purchases and issuances | 32.1 | 52.8
Settlements and reductions | (48.1) | (42.5)
Balance at the end of period | $ 77.8 | $ 92.0

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

X
- Definition Represents total realized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. + References No definition available. + Details
Name: | amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilitiesRealizedGainLossIncludedInEarnings
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents assets and liabilities measured at fair value using significant unobservable inputs (Level 3) which are required for reconciliation purposes of beginning and ending balances. + References No definition available. + Details
Name: | amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilitiesValue
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents purchases, sales, issuances, and settlements (net) which have taken place during the period in relation to assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3). + References No definition available. + Details
Name: | amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetsAndLiabilitiesPurchasesSalesIssuancesSettlements
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents settlements and reductions which have taken place during the period in relation to assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3). + References No definition available. + Details
Name: | amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetsAndLiabilitiesSettlementsAndReductions
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents total unrealized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. + References No definition available. + Details
Name: | amg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisUnrealizedAssetAndLiabilitiesGainLossIncludedInEarnings
Namespace Prefix: | amg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration