Mercer US Small/Mid Cap Equity Fund Mercer Non-US Core Equity Fund Mercer Emerging Markets Equity Fund Mercer Core Fixed Income Fund Mercer Opportunistic Fixed Income Fund Mercer Short Duration Fixed Income Fund Mercer US Small/Mid Cap Equity Fund Mercer Non-US Core Equity Fund Mercer Emerging Markets Equity Fund Mercer Core Fixed Income Fund Mercer Opportunistic Fixed Income Fund Mercer Short Duration Fixed Income Fund Adviser Class Class I Class Y-2 Class Y-3 Adviser Class Class I Class Y-2 Class Y-3 Adviser Class Class I Class Y-2 Class Y-3 Adviser Class Class I Class Y-2 Class Y-3 Adviser Class Class I Class Y-2 Class Y-3 Adviser Class Class I Class Y-2 Class Y-3 Equity Securities Risk [Member] Market Risk [Member] Sovereign Debt Securities Risk [Member] Mortgage-Backed and Asset-Backed Securities Risk [Member] Fixed-Income Securities Risk [Member] Call or Prepayment Risk [Member] U.S. Government Securities Risk [Member] Foreign Investments Risk [Member] High Yield Securities Risk [Member] Floating Rate Loan Risk [Member] Geographic Focus Risk [Member] Currency Exchange Rate Risk [Member] Political and Economic Risk [Member] Foreign Exchange Transaction Risk [Member] Issuer Risk [Member] Large Capitalization Stock Risk [Member] Small and Medium Capitalization Stock Risk [Member] Real Estate Investment Trusts (“REITs”) Risk [Member] Custody Risk [Member] Growth Stock Risk [Member] Value Stock Risk [Member] Derivatives Risk [Member] Emerging Markets Investments Risk [Member] Liquidity Risk [Member] Convertible Securities Risk [Member] Rule 144A Securities Risk [Member] Portfolio Turnover Risk [Member] Management Techniques Risk [Member] Counterparty Risk [Member] Quantitative Model Risk [Member] Frontier Markets Investments Risk [Member] Leverage Risk [Member] Sector Risk [Member] Interest Rate Risk [Member] Credit Risk [Member] Russell 2500® Index (reflects no deduction for fees, expenses, or taxes) MSCI World ex USA IMI Index (net dividends) (reflects no deduction for fees, expenses, or taxes (other than assumed dividend tax)) MSCI Emerging Markets Index (net dividends) (reflects no deduction for fees, expenses, or taxes (other than assumed dividend tax)) Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes) Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes) Secondary Index (reflects no deduction for fees, expenses, or taxes) Bloomberg U.S. 1-3 Year Government/Credit Index (reflects no deduction for fees, expenses, or taxes) C000027786 Member CreditRiskMember index_ Bloomberg_ US_13_ Year_ Government Credit_ Index_reflects_no_deduction_for_fees_expenses_or_taxes Member Floating Rate Loan Risk Member index_ Bloomberg_ US_ Aggregate_ Index_reflects_no_deduction_for_fees_expenses_or_taxes Member doc_ Mercer_ Core_ Fixed_ Income_ Fund Member S000041478 Member doc_ Mercer_ Non US_ Core_ Equity_ Fund Member C000128966 Member Growth Stock Risk Member USGovernment Securities 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