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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate May 31, 2011
Registrant Name dei_EntityRegistrantName JOHN HANCOCK SOVEREIGN BOND FUND
Central Index Key dei_EntityCentralIndexKey 0000045288
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Aug. 30, 2011
Document Effective Date dei_DocumentEffectiveDate Aug. 30, 2011
Prospectus Date rr_ProspectusDate Aug. 30, 2011
Bond Fund | Prospectus Class R6 Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading JOHN HANCOCK BOND FUND
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock To seek a high level of current income consistent with prudent investment risk.
Fees and expenses jhsbf45288_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses you may pay if you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (%) (fees paid directly from your investment)
Annual fund operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual fund operating expenses (%) (expenses that you pay each year as a percentage of the value of your investment)
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates "Other expenses" have been estimated for the first year of operations of the fund's Class R6 shares.
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2012
Expense example rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading Expense example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. Please see below a hypothetical example showing the expenses of a $10,000 investment at the end of the various time frames indicated. The example assumes a 5% average annual return. The example assumes fund expenses will not change over the periods. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading Expenses ($)
Portfolio turnover jhsbf45288_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During its most recent fiscal year, the fund’s portfolio turnover rate was 73% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 73.00%
Strategy [Heading] rr_StrategyHeading Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in a diversified portfolio of bonds. These may include, but are not limited to, corporate bonds and debentures, as well as U.S. government and agency securities. Most of these securities are investment grade, although the fund may invest up to 25% of assets in high-yield bonds rated as low as CC/Ca and their unrated equivalents. There is no limit on the fund’s average maturity.

In managing the fund’s portfolio, the subadviser concentrates on sector allocation, industry allocation and securities selection: deciding which types of bonds and industries to emphasize at a given time, and then which individual bonds to buy. When making sector and industry allocations, the subadviser tries to anticipate shifts in the business cycle, using top-down analysis to determine which sectors and industries may benefit over the next 12 months.

In choosing individual securities, the subadviser uses bottom-up research to find securities that appear comparatively undervalued. The subadviser looks at bonds of all quality levels and maturities from many different issuers, potentially including foreign governments and corporations denominated in U.S. dollars or foreign currencies. The fund will not invest more than 10% of its total assets in securities denominated in foreign currencies.

The fund intends to keep its exposure to interest rate movements generally in line with those of its peers. The fund may invest in mortgage-related securities and derivatives, which include futures contracts on securities and indices; options on futures contracts, securities and indices; and interest rate, foreign currency and credit default swaps, in each case, for the purposes of reducing risk, obtaining efficient market exposure and/or enhancing investment returns. The fund’s investments in U.S. government and agency securities may or may not be supported by the full faith and credit of the United States.

Under normal circumstances, the fund may not invest more than 10% of assets in cash or cash equivalents.
Risk [Heading] rr_RiskHeading Principal risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s shares will go up and down in price, meaning that you could lose money by investing in the fund. Many factors influence a mutual fund’s performance.

Instability in the financial markets has led many governments, including the United States government, to take a number of unprecedented actions designed to support certain financial institutions and segments of the financial markets that have experienced extreme volatility and, in some cases, a lack of liquidity. Federal, state and other governments, and their regulatory agencies or self-regulatory organizations, may take actions that affect the regulation of the instruments in which the fund invests, or the issuers of such instruments, in ways that are unforeseeable. Legislation or regulation may also change the way in which the fund itself is regulated. Such legislation or regulation could limit or preclude the fund’s ability to achieve its investment objective.

Governments or their agencies may also acquire distressed assets from financial institutions and acquire ownership interests in those institutions. The implications of government ownership and disposition of these assets are unclear, and such a program may have positive or negative effects on the liquidity, valuation and performance of the fund’s portfolio holdings. Furthermore, volatile financial markets can expose the fund to greater market and liquidity risk and potential difficulty in valuing portfolio instruments held by the fund.

The fund’s main risk factors are listed below in alphabetical order. Before investing, be sure to read the additional descriptions of these risks beginning on page 5 of the prospectus.

Active management risk The subadviser’s investment strategy may fail to produce the intended result.

Changing distribution levels risk The amount of the distributions paid by the fund generally depends on the amount of income and/or dividends received by the fund on the securities it holds.

Credit and counterparty risk The issuer or guarantor of a fixed-income security, the counterparty to an over-the-counter derivatives contract or a borrower of a fund’s securities may be unable or unwilling to make timely principal, interest or settlement payments, or otherwise to honor its obligations. U.S. government securities are subject to varying degrees of credit risk depending upon the nature of their support. Funds that invest in fixed-income securities are subject to varying degrees of risk that the issuers of the securities will have their credit rating downgraded or will default, potentially reducing a fund’s share price and income level.

Fixed-income securities risk Fixed-income securities are affected by changes in interest rates and credit quality. A rise in interest rates typically causes bond prices to fall. The longer the average maturity of the bonds held by the fund, the more sensitive the fund is likely to be to interest rate changes. There is the possibility that the issuer of the security will not repay all or a portion of the principal borrowed and will not make all interest payments.

Foreign securities risk As compared to U.S. companies, there may be less publicly available information relating to foreign companies. Foreign securities may be subject to foreign taxes. The value of foreign securities is subject to currency fluctuations and adverse political and economic developments.

Hedging, derivatives and other strategic transactions risk Hedging and other strategic transactions may increase the volatility of a fund and, if the transaction is not successful, could result in a significant loss to a fund. The use of derivative instruments could produce disproportionate gains or losses, more than the principal amount invested. Investing in derivative instruments involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional investments and, in a down market, could become harder to value or sell at a fair price.
 
Credit default swaps Counterparty risk, liquidity risk (i.e., the inability to enter into closing transactions), interest-rate risk, risk of default of the underlying reference obligation and risk of disproportionate loss are the principal risks of engaging in transactions involving credit default swaps
 
Foreign currency swaps Counterparty risk, liquidity risk (i.e., the inability to enter into closing transactions), foreign currency risk and risk of disproportionate loss are the principal risks of engaging in transactions involving foreign currency swaps.
 
Futures contracts Counterparty risk, liquidity risk (i.e., the inability to enter into closing transactions) and risk of disproportionate loss are the principal risks of engaging in transactions involving futures contracts.
 
Interest-rate swaps Counterparty risk, liquidity risk (i.e., the inability to enter into closing transactions), interest-rate risk and risk of disproportionate loss are the principal risks of engaging in transactions involving interest-rate swaps.
 
Options Counterparty risk, liquidity risk (i.e., the inability to enter into closing transactions) and risk of disproportionate loss are the principal risks of engaging in transactions involving options. Counterparty risk does not apply to exchange-traded options.

Lower-rated fixed-income securities risk and high-yield securities risk Lower-rated fixed-income securities and high-yield fixed-income securities (commonly known as “junk bonds”) are subject to greater credit-quality risk and risk of default than higher-rated fixed-income securities. These securities may be considered speculative and the value of these securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market or economic developments and can be difficult to resell.

Mortgage-backed and asset-backed securities risk Different types of mortgage-backed securities and asset-backed securities are subject to different combinations of prepayment, extension, interest-rate and/or other market risks.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The fund's shares will go up and down in price, meaning that you could lose money by investing in the fund.
Past performance jhsbf45288_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following performance information in the bar chart and table below illustrates the variability of the fund’s returns and provides some indication of the risks of investing in the fund by showing changes in the fund’s performance from year to year. However, past performance (before and after taxes) does not indicate future results. All figures assume dividend reinvestment. Performance for the fund is updated daily, monthly and quarterly and may be obtained at our Web site: www.jhfunds.com/InstitutionalPerformance, or by calling Signature Services at 1-888-972-8696 between 8:00 A.M. and 7:00 P.M., Eastern Time, on most business days.

Average annual total returns Performance of a broad-based market index is included for comparison.

After-tax returns These reflect the highest individual federal marginal income tax rates in effect as of the date provided and do not reflect any state or local taxes. Your actual after-tax returns may be different. After-tax returns are not relevant to shares held in an IRA, 401(k) or other tax-advantaged investment plan.

Because Class R6 shares of the fund had not commenced operations prior to the date of this prospectus, the returns are those of Class A shares that have been recalculated to apply the estimated gross fees and expenses of Class R6 shares.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information in the bar chart and table below illustrates the variability of the fund’s returns and provides some indication of the risks of investing in the fund by showing changes in the fund’s performance from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture However, past performance (before and after taxes) does not indicate future results.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Performance for the fund is updated daily, monthly and quarterly and may be obtained at our Web site: www.jhfunds.com/InstitutionalPerformance, or by calling Signature Services at 1-888-972-8696 between 8:00 A.M. and 7:00 P.M., Eastern Time, on most business days.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.jhfunds.com/InstitutionalPerformance
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-888-972-8696
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex Average annual total returns Performance of a broad-based market index is included for comparison.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns These reflect the highest individual federal marginal income tax rates in effect as of the date provided and do not reflect any state or local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns may be different. After-tax returns are not relevant to shares held in an IRA, 401(k) or other tax-advantaged investment plan.
Bar Chart, Returns for Class Not Offered in Prospectus [Text] rr_BarChartReturnsForClassNotOfferedInProspectus Because Class R6 shares of the fund had not commenced operations prior to the date of this prospectus, the returns are those of Class A shares that have been recalculated to apply the estimated gross fees and expenses of Class R6 shares.
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Calendar year total returns — Class R6 (%)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Year-to-date total return The fund’s total return for the six months ended June 30, 2011 was 3.69%.

Best quarter: Q3 '09, 11.14%

Worst quarter: Q4 '08, -7.19%
Average Annual Return rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average annual total returns (%) as of 12-31-10
Bond Fund | Prospectus Class R6 Shares | Class R6
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol JHBSX
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R6
Maximum front-end sales charge (load) on purchases as a % of purchase price rr_MaximumCumulativeSalesChargeOverOther none
Maximum deferred sales charge (load) as a % of purchase or sale price, whichever is less rr_MaximumDeferredSalesChargeOverOther none
Annual fund operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R6
Management fee rr_ManagementFeesOverAssets 0.49%
Other expenses rr_OtherExpensesOverAssets 0.10% [1]
Total annual fund operating expenses rr_ExpensesOverAssets 0.59%
Contractual expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [2]
Total annual fund operating expenses after expense reimbursements rr_NetExpensesOverAssets 0.54%
Expense example rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R6
1 Year rr_ExpenseExampleYear01 55
3 Years rr_ExpenseExampleYear03 184
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 7.67%
2002 rr_AnnualReturn2002 7.91%
2003 rr_AnnualReturn2003 8.16%
2004 rr_AnnualReturn2004 5.02%
2005 rr_AnnualReturn2005 2.86%
2006 rr_AnnualReturn2006 4.94%
2007 rr_AnnualReturn2007 5.37%
2008 rr_AnnualReturn2008 (11.52%)
2009 rr_AnnualReturn2009 29.08%
2010 rr_AnnualReturn2010 13.40%
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-date total return The fund’s total return for the six months ended
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2011
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.69%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.14%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.19%)
Bond Fund | Prospectus Class R6 Shares | before tax | Class R6
  
Average Annual Return rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R6
Label rr_AverageAnnualReturnLabel before tax
1 Year rr_AverageAnnualReturnYear01 13.40%
5 Year rr_AverageAnnualReturnYear05 7.45%
10 Year rr_AverageAnnualReturnYear10 6.87%
Bond Fund | Prospectus Class R6 Shares | After tax on distributions | Class R6
  
Average Annual Return rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R6
Label rr_AverageAnnualReturnLabel After tax on distributions
1 Year rr_AverageAnnualReturnYear01 11.09%
5 Year rr_AverageAnnualReturnYear05 5.24%
10 Year rr_AverageAnnualReturnYear10 4.77%
Bond Fund | Prospectus Class R6 Shares | After tax on distributions, with sale | Class R6
  
Average Annual Return rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R6
Label rr_AverageAnnualReturnLabel After tax on distributions, with sale
1 Year rr_AverageAnnualReturnYear01 8.65%
5 Year rr_AverageAnnualReturnYear05 5.00%
10 Year rr_AverageAnnualReturnYear10 4.61%
Bond Fund | Prospectus Class R6 Shares | Barclays Capital Government/Credit Bond Index
  
Average Annual Return rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays Capital Government/Credit Bond Index
1 Year rr_AverageAnnualReturnYear01 6.59%
5 Year rr_AverageAnnualReturnYear05 5.56%
10 Year rr_AverageAnnualReturnYear10 5.83%
[1] "Other expenses" have been estimated for the first year of operations of the fund's Class R6 shares.
[2] The adviser has contractually agreed to waive a portion of its management fee and/or reimburse or pay operating expenses of the fund in order to reduce the total annual fund operating expenses for Class R6 shares by 0.05% of the fund's average daily net assets. These fee waivers and/or reimbursements expire on September 30, 2012, unless renewed by mutual agreement of the fund and the adviser based upon a determination that this is appropriate under the circumstances at the time.