XML 56 R53.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Fair Value Measurements (Details 3) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2012 | Jun. 30, 2011 | Jun. 30, 2012 | Jun. 30, 2011
Changes in level 3 assets and liabilities |  |  |  |
Transfers of financial assets from level 1 to level 2 |  |  | $ 2.0 |
Other investments |  |  |  |
Changes in level 3 assets and liabilities |  |  |  |
Balance at the beginning of the period | 107.5 | 93.6 | 103.4 | 85.8
Net realized gains/losses | (0.9) | (0.1) | (1.7) | 1.0
Net unrealized gains/losses relating to instruments still held at the reporting date | 3.6 | 4.9 | 6.1 | 10.5
Purchases and issuances | 5.2 | 5.8 | 10.0 | 8.6
Settlements and reductions | (2.4) | (2.2) | (4.8) | (3.9)
Balance at the end of period | 113.0 | 102.0 | 113.0 | 102.0
Contingent payment arrangements |  |  |  |
Changes in level 3 assets and liabilities |  |  |  |
Balance at the beginning of the period | 83.1 | 83.0 | 87.1 | 77.6
Net unrealized gains/losses relating to instruments still held at the reporting date | (45.4) | 4.0 | (49.4) | 9.4
Purchases and issuances | 24.8 |  | 24.8 |
Settlements and reductions |  | (1.7) |  | (1.7)
Balance at the end of period | 62.5 | 85.3 | 62.5 | 85.3
Obligations to related parties |  |  |  |
Changes in level 3 assets and liabilities |  |  |  |
Balance at the beginning of the period | 77.6 | 67.9 | 92.0 | 79.6
Net realized gains/losses | 0.7 | 0.3 | 0.5 | 0.6
Net unrealized gains/losses relating to instruments still held at the reporting date | (0.2) | 1.1 | 0.8 | 3.6
Purchases and issuances | 6.0 | 3.4 | 20.3 | 13.0
Settlements and reductions | (4.6) | (1.5) | (34.1) | (25.6)
Balance at the end of period | $ 79.5 | $ 71.2 | $ 79.5 | $ 71.2

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

X
- Definition The amount of the transfers of assets or liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueLevel1ToLevel2TransfersAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration