This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2025 to April 30, 2026.

Additional Information [Text Block]

You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php. You can also request this information by contacting us at 1-800-262-1122.

Additional Information Phone Number

1-800-262-1122

Additional Information Website

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Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class A	$50	1.00%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 50

Expense Ratio, Percent

1.00%

^[1]

AssetsNet

$ 4,084,083,897

Holdings Count | Holding

425

InvestmentCompanyPortfolioTurnover

20.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Table Summary
Total Net Assets	$4,084,083,897
# of Portfolio Holdings	425
Portfolio Turnover Rate	20%

Holdings [Text Block]

Asset Allocation (% of total investments)

Table Summary
Value	Value
Other^{Footnote Reference†}	2.8%
Short-Term Investments	3.2%
Senior Floating-Rate Loans	9.7%
Corporate Bonds	84.3%

Footnote	Description
Footnote^†	Investment types less than 1% each

Credit Quality (% of total investments)^{Footnote Referencea}

Table Summary
Value	Value
Not Rated	5.4%
CCC or Lower	9.2%
B	37.3%
BB	45.3%
BBB	2.8%

Footnote

Description

Footnote^a

Excludes Short-Term Investments. Ratings are based on Moody’s Investors Service, Inc. (“Moody’s”), S&P Global Ratings (“S&P”) or Fitch Ratings (“Fitch”). This breakdown assigns a numeric equivalent to the ratings from the aforementioned agencies and the mean is rounded to the nearest integer and converted to an equivalent S&P rating ranging from AAA, being the highest, to D, being the lowest. Ratings of BBB or higher are considered to be investment-grade quality. Holdings designated as “Not Rated” (if any) are not rated by the national ratings agencies stated above.

Material Fund Change [Text Block]

Updated Prospectus Phone Number

1-800-262-1122

C000013486

Shareholder Report [Line Items]

Fund Name

Eaton Vance Income Fund of Boston

Class Name

Class C

Trading Symbol

ECIBX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2025 to April 30, 2026.

Additional Information [Text Block]

You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php. You can also request this information by contacting us at 1-800-262-1122.

Additional Information Phone Number

1-800-262-1122

Additional Information Website

Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class C	$87	1.75%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 87

Expense Ratio, Percent

1.75%

^[2]

AssetsNet

$ 4,084,083,897

Holdings Count | Holding

425

InvestmentCompanyPortfolioTurnover

20.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Table Summary
Total Net Assets	$4,084,083,897
# of Portfolio Holdings	425
Portfolio Turnover Rate	20%

Holdings [Text Block]

Asset Allocation (% of total investments)

Table Summary
Value	Value
Other^{Footnote Reference†}	2.8%
Short-Term Investments	3.2%
Senior Floating-Rate Loans	9.7%
Corporate Bonds	84.3%

Footnote	Description
Footnote^†	Investment types less than 1% each

Credit Quality (% of total investments)^{Footnote Referencea}

Table Summary
Value	Value
Not Rated	5.4%
CCC or Lower	9.2%
B	37.3%
BB	45.3%
BBB	2.8%

Footnote

Description

Footnote^a

Material Fund Change [Text Block]

Updated Prospectus Phone Number

1-800-262-1122

C000013488

Shareholder Report [Line Items]

Fund Name

Eaton Vance Income Fund of Boston

Class Name

Class I

Trading Symbol

EIBIX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2025 to April 30, 2026.

Additional Information [Text Block]

You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php. You can also request this information by contacting us at 1-800-262-1122.

Additional Information Phone Number

1-800-262-1122

Additional Information Website

Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class I	$38	0.75%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 38

Expense Ratio, Percent

0.75%

^[3]

AssetsNet

$ 4,084,083,897

Holdings Count | Holding

425

InvestmentCompanyPortfolioTurnover

20.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Table Summary
Total Net Assets	$4,084,083,897
# of Portfolio Holdings	425
Portfolio Turnover Rate	20%

Holdings [Text Block]

Asset Allocation (% of total investments)

Table Summary
Value	Value
Other^{Footnote Reference†}	2.8%
Short-Term Investments	3.2%
Senior Floating-Rate Loans	9.7%
Corporate Bonds	84.3%

Footnote	Description
Footnote^†	Investment types less than 1% each

Credit Quality (% of total investments)^{Footnote Referencea}

Table Summary
Value	Value
Not Rated	5.4%
CCC or Lower	9.2%
B	37.3%
BB	45.3%
BBB	2.8%

Footnote

Description

Footnote^a

Material Fund Change [Text Block]

Updated Prospectus Phone Number

1-800-262-1122

C000013487

Shareholder Report [Line Items]

Fund Name

Eaton Vance Income Fund of Boston

Class Name

Class R

Trading Symbol

ERIBX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2025 to April 30, 2026.

Additional Information [Text Block]

You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php. You can also request this information by contacting us at 1-800-262-1122.

Additional Information Phone Number

1-800-262-1122

Additional Information Website

Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class R	$63	1.25%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 63

Expense Ratio, Percent

1.25%

^[4]

AssetsNet

$ 4,084,083,897

Holdings Count | Holding

425

InvestmentCompanyPortfolioTurnover

20.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Table Summary
Total Net Assets	$4,084,083,897
# of Portfolio Holdings	425
Portfolio Turnover Rate	20%

Holdings [Text Block]

Asset Allocation (% of total investments)

Table Summary
Value	Value
Other^{Footnote Reference†}	2.8%
Short-Term Investments	3.2%
Senior Floating-Rate Loans	9.7%
Corporate Bonds	84.3%

Footnote	Description
Footnote^†	Investment types less than 1% each

Credit Quality (% of total investments)^{Footnote Referencea}

Table Summary
Value	Value
Not Rated	5.4%
CCC or Lower	9.2%
B	37.3%
BB	45.3%
BBB	2.8%

Footnote

Description

Footnote^a

Material Fund Change [Text Block]

Updated Prospectus Phone Number

1-800-262-1122

C000142452

Shareholder Report [Line Items]

Fund Name

Eaton Vance Income Fund of Boston

Class Name

Class R6

Trading Symbol

EIBRX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2025 to April 30, 2026.

Additional Information [Text Block]

You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php. You can also request this information by contacting us at 1-800-262-1122.

Additional Information Phone Number

1-800-262-1122

Additional Information Website

Expenses [Text Block]