Vanguard Balanced Index Fund Vanguard Balanced Index Fund - Investor Shares Vanguard Balanced Index Fund - Admiral Shares Balanced Composite Index MSCI US Broad Market Index Spliced Total Stock Market Index Spliced Barclays U.S. Aggregate Float Adjusted Index Dow Jones U.S. Total Stock Market Float Adjusted Index Balanced Composite Index MSCI US Broad Market Index Spliced Total Stock Market Index Spliced Barclays U.S. Aggregate Float Adjusted Index Dow Jones U.S. Total Stock Market Float Adjusted Index Institutional Participant Participant: Retail Signal Acquired Fund Fees and Expenses (based on estimates) Acquired Fund Fees and Expenses Return After Taxes on Distributions and Sale of Fund Shares Return After Taxes on Distributions Annual Fund Operating Expenses [Expenses that you pay each year as a percentage of the value of your investment] 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Annual Return Caption Annual Return Column Annual Return Inception Date Average Annual Return Caption Average Annual Return Column Inception Date Average Annual Return Label Since Inception One Year Five Years Ten Years Bar Chart and Performance Table Bar Chart and Performance Table Section: Bar Chart Closing: Bar Chart Closing Bar Chart Does Not Reflect Sales Loads Bar Chart Footnotes Bar Chart Bar Chart Highest Quarterly Return Bar Chart Highest Quarterly Return Date Bar Chart Lowest Quarter Return Bar Chart Lowest Quarter Return Date Bar Chart Narrative: Bar Chart Narrative Bar Chart Reason Selected Class Different from Immediately Preceding Period Bar Chart Returns for Class Not Offered in Prospectus Annual Total Return Bar Chart: Year to Date Return Date Dividend Expenses on Securities Sold Short Borrowing Expenses on Securities Sold Short Other Operating Expenses 12b-1 Distribution Fee Distribution or Similar (Non 12b-1) Fees / Assets Exchange Fee Exchange Fee / Redemption Expense Breakpoint Discounts Expense Breakpoint, Minimum Investment Required Expense Example Expense Example, with Redemption, Caption Expense Example, with Redemption, Column Expense Example Heading Expense Example Closing Expense Example Footnotes EXAMPLE Expense Example, Narrative [Text Block] Expense Example, No Redemption: Expense Example, no Redemption, Caption Expense Example, no Redemption, Column Expense Example, No Redemption Narrative [Text Block] Expense Example, No Redemption 1 YEAR 3 YEAR 5 YEAR 10 YEAR Expense Example, With Redemption 1 YEAR, 3 YEAR, 5 YEAR, 10 YEAR, Expense Exchange Traded Fund Commissions Expense Footnotes: Expense Footnotes Expenses Heading Fees and Expenses of the Fund Expenses: Deferred Charges Narrative Expenses Explanation of Nonrecurring Account Fee Expenses Not Correlated to Ratio Due to Acquired Fund Fees Expenses Other Expenses Had Extraordinary Expenses Been Included Net Expenses / Assets Expenses / Assets Range of Exchange Fees Narrative Expenses Represent Both Master and Feeder Expenses Restated to Reflect Current Fee Waiver or Reimbursement Fee Waiver or Reimbursement, Date of Termination Highest Quarterly Return Label Index No Deduction for Fees, Expenses, Taxes Lowest Quarterly Return Label Management Expenses Market Index Performance Account Service Fee (for fund account balances below $10,000) Maximum Account Fee / Assets Sales charge (load) imposed on purchases Purchase Fee Maximum deferred sales charge (load) (as a percentage of the amount redeemed) Maximum Deferred Sales Charge / Other Maximum Sales Charge Imposed on Purchases / Offering Price Sales charge (load) imposed on reinvested dividends 7-Day Tax Equivalent Yield Money Market Seven Day Yield Money Market 7-Day Yield Caption Money Market 7-Day Yield Column 7-Day Yield Phone Total Annual Fund Operating Expenses Net Expenses / Assets: Investment objective: Investment objective Secondary objectives Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment) Operating Expenses Caption Operating Expenses Column Other Expenses, New Fund, Based on Estimates Other Expenses Other Expenses: Performance Additional Market Index Performance Availability Phone Performance Availability Website Address Performance Information Illustrates Variability of Returns Performance Measure [Axis] Return Before Taxes Performance Narrative: Performance Narrative Performance One Year or Less Past Performance Does Not Indiciate Future Returns Performance Table Closing: Performance Table Closing Performance Table Does Reflect Sales Loads Performance Table Explains why after Tax Higher Performance Table Footnotes, Reason Performance Information for Class Different from Immediately Preceding Period Performance Table Footnotes Bar Chart and Performance Table: Performance Table Market Index Changed Performance Table Narrative Performance Table Not Relevant to Tax Deferred One Class of After-Tax Shown Bar Chart and Performance Table Section Performance Performance Table Uses Highest Federal Rate Portfolio Turnover: Portfolio Turnover Heading PortfolioTurnover, Rate Portfolio Turnover Prospectus Date Prospectus: Share Class [Axis] Prospectus [Table] Redemption Fee USD Redemption Fee Risk Risk Caption Risk Closing [Text Block] Risk Column Risk Footnotes Risk: May Lose Money Money Market Fund Risk Narrative Nondiversified Not Insured Depository Institution Risk/Return: Risk/Return Detail [Table] Risk/Return RiskSection: Share Classes Other Shareholder Fees (fees paid directly from your investment] Shareholder Fees Caption Shareholder Fees Column Shareholder Fees (Fees paid directly from your investment) [Table] Strategy: StrategyNarrative Strategy Portfolio Concentration Strategy Section: 30-DayTax Equivalent Yield Thirty Day Yield: 30-Day Yield Caption 30-Day Yield Column 30-Day Yield Phone Year to Date Return Label Series [Axis] All Series All Prospectuses Prospectus [Axis] Document Creation Date Document Effective Date Document Period End Date Document Type Registrant Name Central Index Key Amendment Flag Amendment Description Transaction Fee on Conversion to ETF Shares Transaction Fee On Purchases and Sales Transaction Fee On Reinvested Dividends Average Annual Returns for Periods Ended December 31, 2011 Supplement Text: Supplement Text Redemption Fee Parenthetical Purchase Fee Parenthetical Based on Market Value Comparative Benchmark Fund Operating Expenses Excluding AFFE Acquired Fund Fees and Expenses Return Before Taxes Dividend Expenses on Securities Sold Short Borrowing Expenses on Securities Sold Short Other Operating Expenses 12b-1 Distribution Fee Management Expenses Account Service Fee (for fund account balances below $10,000) Sales Charge (Load) Imposed on Purchases Purchase Fee Sales Charge (Load) Imposed on Reinvested Dividends Total Annual Fund Operating Expenses Other Expenses Redemption Fee Acquired Fund Fees and Expenses Return Before Taxes Dividend Expenses on Securities Sold Short Borrowing Expenses on Securities Sold Short Other Operating Expenses 12b-1 Distribution Fee Management Expenses Account Service Fee (for fund account balances below $10,000) Sales Charge (Load) Imposed on Purchases Purchase Fee Sales Charge (Load) Imposed on Reinvested Dividends Total Annual Fund Operating Expenses Other Expenses Redemption Fee