XML 94 R65.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value Measurements - Fair Value of Certain Investments Based on NAV (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 149,222us-gaap_AlternativeInvestmentsFairValueDisclosure 151,269us-gaap_AlternativeInvestmentsFairValueDisclosure
Unfunded Commitments 18,676us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments 27,135us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
Alternative Investment Funds [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 31,042us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= us-gaap_HedgeFundsEquityMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember		 31,837us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= us-gaap_HedgeFundsEquityMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember
Alternative Investment Funds [Member] | Funds of Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 475us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_FundsOfFundsMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember		 475us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_FundsOfFundsMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember
Alternative Investment Funds [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 3,188us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_OtherFundsMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember		 4,718us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_OtherFundsMember
/ us-gaap_InvestmentTypeAxis
= laz_AlternativeInvestmentsMember
Alternative Investment Funds [Member] | Weekly [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency weekly (3%) weekly (1%)
Alternative Investment Funds [Member] | Weekly [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency weekly (15%) weekly (17%)
Alternative Investment Funds [Member] | Monthly [Member] | Funds of Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency monthly (98%) monthly (95%)
Alternative Investment Funds [Member] | Monthly [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency monthly (86%) monthly (92%)
Alternative Investment Funds [Member] | Monthly [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency monthly (66%) monthly (65%)
Alternative Investment Funds [Member] | Quarterly [Member] | Funds of Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency quarterly (2%) quarterly (5%)
Alternative Investment Funds [Member] | Quarterly [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency quarterly (19%) quarterly (18%)
Alternative Investment Funds [Member] | Daily [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency daily (11%) daily (7%)
Alternative Investment Funds [Member] | Minimum [Member] | Funds of Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 30 days 30 days
Alternative Investment Funds [Member] | Minimum [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 30 days 30 days
Alternative Investment Funds [Member] | Minimum [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 30 days 30 days
Alternative Investment Funds [Member] | Maximum [Member] | Funds of Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 90 days 90 days
Alternative Investment Funds [Member] | Maximum [Member] | Other [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 60 days 60 days
Alternative Investment Funds [Member] | Maximum [Member] | Hedge Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 60 days 90 days
Debt Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 4us-gaap_AlternativeInvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= laz_DebtFundsMember		 4us-gaap_AlternativeInvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= laz_DebtFundsMember
Investments Redeemable, Redemption Notice Period 30 days 30 days
Debt Funds [Member] | Daily [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency daily (100%) daily (100%)
Equity Funds [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 43us-gaap_AlternativeInvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember		 42us-gaap_AlternativeInvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember
Equity Funds [Member] | Monthly [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency monthly (58%) monthly (58%)
Equity Funds [Member] | Quarterly [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency quarterly (28%) quarterly (29%)
Equity Funds [Member] | Daily [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Frequency daily (14%) daily (13%)
Equity Funds [Member] | Minimum [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 30 days 30 days
Equity Funds [Member] | Maximum [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments Redeemable, Redemption Notice Period 90 days 90 days
Private Equity Funds [Member] | Equity Growth [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 75,578us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 70,054us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Unfunded Commitments 18,676us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 27,135us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
% of Fair Value Not Redeemable 100.00%laz_PercentageOfFairValueNotRedeemable
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 100.00%laz_PercentageOfFairValueNotRedeemable
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Estimated Liquidation Period of Investments Not Redeemable, % Next 5 Years 10.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableNextFiveYears
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 17.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableNextFiveYears
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Estimated Liquidation Period of Investments Not Redeemable, % 5-10 Years 63.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableFiveToTenYears
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 60.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableFiveToTenYears
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Estimated Liquidation Period of Investments Not Redeemable, % Thereafter 27.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableThereafter
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 23.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableThereafter
/ invest_InvestmentAxis
= laz_EquityGrowthMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Private Equity Funds [Member] | Mezzanine Debt [Member]    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 38,892us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 44,139us-gaap_AlternativeInvestmentsFairValueDisclosure
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
% of Fair Value Not Redeemable 100.00%laz_PercentageOfFairValueNotRedeemable
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 100.00%laz_PercentageOfFairValueNotRedeemable
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember
Estimated Liquidation Period of Investments Not Redeemable, % Thereafter 100.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableThereafter
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember		 100.00%laz_PercentageOfEstimatedLiquidationPeriodOfInvestmentsNotRedeemableThereafter
/ invest_InvestmentAxis
= laz_MezzanineDebtMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_PrivateEquityFundsMember