This semi-annual shareholder report contains important information about the Eaton Vance Income Fund of Boston for the period of November 1, 2024 to April 30, 2025.

Shareholder Report Annual or Semi-Annual

Semi-Annual Shareholder Report

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)

Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class A	$48	0.96%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 48

Expense Ratio, Percent

0.96%

^[1]

AssetsNet

$ 5,763,371,656

Holdings Count | Holding

432

InvestmentCompanyPortfolioTurnover

15.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$5,763,371,656
# of Portfolio Holdings	432
Portfolio Turnover Rate	15%

Holdings [Text Block]

Asset Allocation (% of total investments)

Value	Value
Other^{Footnote Reference†}	1.9%
Short-Term Investments	3.6%
Senior Floating-Rate Loans	7.0%
Corporate Bonds	87.5%

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

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

Value	Value
Not Rated	2.6%
CCC or Lower	10.9%
B	40.1%
BB	44.7%
BBB	1.7%

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, 2024 to April 30, 2025.

Shareholder Report Annual or Semi-Annual

Semi-Annual Shareholder Report

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)

Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class C	$85	1.71%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 85

Expense Ratio, Percent

1.71%

^[2]

AssetsNet

$ 5,763,371,656

Holdings Count | Holding

432

InvestmentCompanyPortfolioTurnover

15.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$5,763,371,656
# of Portfolio Holdings	432
Portfolio Turnover Rate	15%

Holdings [Text Block]

Asset Allocation (% of total investments)

Value	Value
Other^{Footnote Reference†}	1.9%
Short-Term Investments	3.6%
Senior Floating-Rate Loans	7.0%
Corporate Bonds	87.5%

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

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

Value	Value
Not Rated	2.6%
CCC or Lower	10.9%
B	40.1%
BB	44.7%
BBB	1.7%

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, 2024 to April 30, 2025.

Shareholder Report Annual or Semi-Annual

Semi-Annual Shareholder Report

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)

Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class I	$36	0.72%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 36

Expense Ratio, Percent

0.72%

^[3]

AssetsNet

$ 5,763,371,656

Holdings Count | Holding

432

InvestmentCompanyPortfolioTurnover

15.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$5,763,371,656
# of Portfolio Holdings	432
Portfolio Turnover Rate	15%

Holdings [Text Block]

Asset Allocation (% of total investments)

Value	Value
Other^{Footnote Reference†}	1.9%
Short-Term Investments	3.6%
Senior Floating-Rate Loans	7.0%
Corporate Bonds	87.5%

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

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

Value	Value
Not Rated	2.6%
CCC or Lower	10.9%
B	40.1%
BB	44.7%
BBB	1.7%

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, 2024 to April 30, 2025.

Shareholder Report Annual or Semi-Annual

Semi-Annual Shareholder Report

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)

Class Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Class R	$61	1.21%^{Footnote Reference1}

Footnote	Description
Footnote¹	Annualized

Expenses Paid, Amount

$ 61

Expense Ratio, Percent

1.21%

^[4]

AssetsNet

$ 5,763,371,656

Holdings Count | Holding

432

InvestmentCompanyPortfolioTurnover

15.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$5,763,371,656
# of Portfolio Holdings	432
Portfolio Turnover Rate	15%

Holdings [Text Block]

Asset Allocation (% of total investments)

Value	Value
Other^{Footnote Reference†}	1.9%
Short-Term Investments	3.6%
Senior Floating-Rate Loans	7.0%
Corporate Bonds	87.5%

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

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

Value	Value
Not Rated	2.6%
CCC or Lower	10.9%
B	40.1%
BB	44.7%
BBB	1.7%

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, 2024 to April 30, 2025.

Shareholder Report Annual or Semi-Annual

Semi-Annual Shareholder Report

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]