This semi-annual shareholder report contains important information about Loomis Sayles Fixed Income Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

You can find additional information about the Fund at im.natixis.com/funddocuments. You can also request this information by contacting us at (800) 633-3330 or by contacting your financial intermediary directly.

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Institutional Class	$31	0.61%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 31

Expense Ratio, Percent

0.61%

AssetsNet

$ 433,766,125

Holdings Count | Holding

717

Advisory Fees Paid, Amount

$ 1,095,678

InvestmentCompanyPortfolioTurnover

37.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$433,766,125
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	717
Portfolio Turnover Rate	37%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$1,095,678

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	41.7%
Short-Term Investments	3.7%
Aerospace & Defense	3.2%
Independent Energy	3.2%
Sovereigns	3.4%
ABS Car Loan	3.6%
ABS Home Equity	3.7%
Banking	4.0%
Finance Companies	4.3%
Cable Satellite	5.7%
ABS Other	5.8%
Technology	6.1%
Treasuries	11.5%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	2.2
US Treasury	9.3
Not rated^{Footnote Reference^}	17.1
C	0.1
CC	1.0
CCC	1.1
B	4.3
BB	14.7
BBB	42.4
A	5.7
AA	1.2
AAA	0.9

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018127

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Global Bond Fund

Class Name

Institutional Class

Trading Symbol

LSGBX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Global Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Institutional Class	$34	0.69%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 34

Expense Ratio, Percent

0.69%

AssetsNet

$ 330,590,782

Holdings Count | Holding

239

Advisory Fees Paid, Amount

$ 789,363

InvestmentCompanyPortfolioTurnover

27.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$330,590,782
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	239
Portfolio Turnover Rate	27%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$789,363

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	25.8%
Technology	3.0%
Government Owned - No Guarantee	3.6%
Local Authorities	5.0%
Banking	7.5%
Mortgage Related	12.3%
Treasuries	42.9%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Country Weightings

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	29.0%
Germany	3.1%
Canada	4.6%
Spain	4.7%
United Kingdom	4.7%
France	5.6%
China	7.4%
Japan	7.6%
United States	33.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	2.5
US Treasury	4.3
Not rated^{Footnote Reference^}	10.3
BB	5.6
BBB	24.1
A	20.3
AA	27.1
AAA	5.8

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018128

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Global Bond Fund

Class Name

Retail Class

Trading Symbol

LSGLX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Global Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Retail Class	$46	0.94%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 46

Expense Ratio, Percent

0.94%

AssetsNet

$ 330,590,782

Holdings Count | Holding

239

Advisory Fees Paid, Amount

$ 789,363

InvestmentCompanyPortfolioTurnover

27.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$330,590,782
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	239
Portfolio Turnover Rate	27%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$789,363

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	25.8%
Technology	3.0%
Government Owned - No Guarantee	3.6%
Local Authorities	5.0%
Banking	7.5%
Mortgage Related	12.3%
Treasuries	42.9%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Country Weightings

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	29.0%
Germany	3.1%
Canada	4.6%
Spain	4.7%
United Kingdom	4.7%
France	5.6%
China	7.4%
Japan	7.6%
United States	33.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	2.5
US Treasury	4.3
Not rated^{Footnote Reference^}	10.3
BB	5.6
BBB	24.1
A	20.3
AA	27.1
AAA	5.8

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000125494

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Global Bond Fund

Class Name

Class N

Trading Symbol

LSGNX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Global Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Class N	$31	0.64%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 31

Expense Ratio, Percent

0.64%

AssetsNet

$ 330,590,782

Holdings Count | Holding

239

Advisory Fees Paid, Amount

$ 789,363

InvestmentCompanyPortfolioTurnover

27.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$330,590,782
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	239
Portfolio Turnover Rate	27%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$789,363

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	25.8%
Technology	3.0%
Government Owned - No Guarantee	3.6%
Local Authorities	5.0%
Banking	7.5%
Mortgage Related	12.3%
Treasuries	42.9%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Country Weightings

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	29.0%
Germany	3.1%
Canada	4.6%
Spain	4.7%
United Kingdom	4.7%
France	5.6%
China	7.4%
Japan	7.6%
United States	33.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	2.5
US Treasury	4.3
Not rated^{Footnote Reference^}	10.3
BB	5.6
BBB	24.1
A	20.3
AA	27.1
AAA	5.8

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018129

Shareholder Report [Line Items]

Fund Name

Loomis Sayles High Income Opportunities Fund

Class Name

Institutional Class

Trading Symbol

LSIOX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles High Income Opportunities Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

You can find additional information about the Fund at loomissayles.com/website/intermediary-advisory/prospectuses-and-fund-reports. You can also request this information by contacting us at (800) 633-3330 or by contacting your financial intermediary directly.

Additional Information Phone Number

(800) 633-3330

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
Institutional Class	$0	0.00%

Expenses Paid, Amount

$ 0

Expense Ratio, Percent

0.00%

AssetsNet

$ 304,398,179

Holdings Count | Holding

451

Advisory Fees Paid, Amount

$ 0

InvestmentCompanyPortfolioTurnover

49.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$304,398,179
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	451
Portfolio Turnover Rate	49%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$0

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	41.2%
Short-Term Investments	8.2%
Pharmaceuticals	3.0%
Metals & Mining	3.5%
Healthcare	3.7%
Independent Energy	5.9%
Property & Casualty Insurance	6.0%
Midstream	6.7%
Cable Satellite	9.6%
Technology	12.1%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	4.5
Not rated^{Footnote Reference^}	9.1
C	0.5
CC	0.7
CCC	3.9
B	26.9
BB	50.5
BBB	3.8
A	0.1

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018130

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Inflation Protected Securities Fund

Class Name

Institutional Class

Trading Symbol

LSGSX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Inflation Protected Securities Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Institutional Class	$20	0.40%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 20

Expense Ratio, Percent

0.40%

AssetsNet

$ 106,185,583

Holdings Count | Holding

Advisory Fees Paid, Amount

$ 22,648

InvestmentCompanyPortfolioTurnover

21.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$106,185,583
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	47
Portfolio Turnover Rate	21%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$22,648

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	4.4%
Short-Term Investments	4.6%
Banking	3.5%
Treasuries	87.5%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	4.6
US Treasury	87.5
Not rated^{Footnote Reference^}	1.1
BB	0.7
BBB	3.9
A	2.0
AA	0.2

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000089752

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Inflation Protected Securities Fund

Class Name

Retail Class

Trading Symbol

LIPRX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Inflation Protected Securities Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Retail Class	$32	0.65%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 32

Expense Ratio, Percent

0.65%

AssetsNet

$ 106,185,583

Holdings Count | Holding

Advisory Fees Paid, Amount

$ 22,648

InvestmentCompanyPortfolioTurnover

21.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$106,185,583
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	47
Portfolio Turnover Rate	21%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$22,648

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	4.4%
Short-Term Investments	4.6%
Banking	3.5%
Treasuries	87.5%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	4.6
US Treasury	87.5
Not rated^{Footnote Reference^}	1.1
BB	0.7
BBB	3.9
A	2.0
AA	0.2

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000182246

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Inflation Protected Securities Fund

Class Name

Class N

Trading Symbol

LIPNX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Inflation Protected Securities Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Class N	$17	0.35%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 17

Expense Ratio, Percent

0.35%

AssetsNet

$ 106,185,583

Holdings Count | Holding

Advisory Fees Paid, Amount

$ 22,648

InvestmentCompanyPortfolioTurnover

21.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$106,185,583
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	47
Portfolio Turnover Rate	21%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$22,648

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	4.4%
Short-Term Investments	4.6%
Banking	3.5%
Treasuries	87.5%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	4.6
US Treasury	87.5
Not rated^{Footnote Reference^}	1.1
BB	0.7
BBB	3.9
A	2.0
AA	0.2

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018131

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Institutional High Income Fund

Class Name

Institutional Class

Trading Symbol

LSHIX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Institutional High Income Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Institutional Class	$36	0.72%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 36

Expense Ratio, Percent

0.72%

AssetsNet

$ 267,087,697

Holdings Count | Holding

420

Advisory Fees Paid, Amount

$ 886,612

InvestmentCompanyPortfolioTurnover

51.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$267,087,697
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	420
Portfolio Turnover Rate	51%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$886,612

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	45.7%
Short-Term Investments	4.1%
Healthcare	3.7%
Pharmaceuticals	3.7%
Metals & Mining	3.7%
Independent Energy	5.5%
Property & Casualty Insurance	5.7%
Midstream	6.0%
Cable Satellite	10.8%
Technology	11.1%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including forward foreign currency contracts and futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	3.6
Not rated^{Footnote Reference^}	13.9
C	0.6
CC	0.7
CCC	4.8
B	27.6
BB	46.3
BBB	2.5

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018132

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Intermediate Duration Bond Fund

Class Name

Class Y

Trading Symbol

LSDIX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Intermediate Duration Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments. You can also request the information by contacting us at (800) 225-5478 or by contacting your financial intermediary directly.

Additional Information Phone Number

(800) 225-5478

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^{Footnote Reference†}
Class Y	$20	0.40%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 20

Expense Ratio, Percent

0.40%

AssetsNet

$ 238,699,721

Holdings Count | Holding

527

Advisory Fees Paid, Amount

$ 190,088

InvestmentCompanyPortfolioTurnover

72.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets$238,699,721
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)527
Portfolio Turnover Rate72%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)$190,088

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	21.5%
Electric	3.4%
Finance Companies	3.5%
Automotive	4.3%
ABS Other	4.4%
Life Insurance	4.4%
Non-Agency Commercial Mortgage-Backed Securities	8.0%
ABS Car Loan	12.7%
Banking	13.7%
Treasuries	24.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	0.8
US Treasury	24.5
Not rated^{Footnote Reference^}	14.1
BBB	24.5
A	19.3
AA	6.7
AAA	10.1

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000089753

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Intermediate Duration Bond Fund

Class Name

Class A

Trading Symbol

LSDRX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Intermediate Duration Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 225-5478

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^{Footnote Reference†}
Class A	$33	0.65%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 33

Expense Ratio, Percent

0.65%

AssetsNet

$ 238,699,721

Holdings Count | Holding

527

Advisory Fees Paid, Amount

$ 190,088

InvestmentCompanyPortfolioTurnover

72.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets$238,699,721
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)527
Portfolio Turnover Rate72%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)$190,088

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	21.5%
Electric	3.4%
Finance Companies	3.5%
Automotive	4.3%
ABS Other	4.4%
Life Insurance	4.4%
Non-Agency Commercial Mortgage-Backed Securities	8.0%
ABS Car Loan	12.7%
Banking	13.7%
Treasuries	24.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	0.8
US Treasury	24.5
Not rated^{Footnote Reference^}	14.1
BBB	24.5
A	19.3
AA	6.7
AAA	10.1

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000173092

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Intermediate Duration Bond Fund

Class Name

Class C

Trading Symbol

LSCDX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Intermediate Duration Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 225-5478

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^{Footnote Reference†}
Class C	$70	1.40%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 70

Expense Ratio, Percent

1.40%

AssetsNet

$ 238,699,721

Holdings Count | Holding

527

Advisory Fees Paid, Amount

$ 190,088

InvestmentCompanyPortfolioTurnover

72.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets$238,699,721
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)527
Portfolio Turnover Rate72%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)$190,088

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	21.5%
Electric	3.4%
Finance Companies	3.5%
Automotive	4.3%
ABS Other	4.4%
Life Insurance	4.4%
Non-Agency Commercial Mortgage-Backed Securities	8.0%
ABS Car Loan	12.7%
Banking	13.7%
Treasuries	24.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	0.8
US Treasury	24.5
Not rated^{Footnote Reference^}	14.1
BBB	24.5
A	19.3
AA	6.7
AAA	10.1

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000211126

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Intermediate Duration Bond Fund

Class Name

Class N

Trading Symbol

LSDNX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Intermediate Duration Bond Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 225-5478

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^{Footnote Reference†}
Class N	$18	0.35%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 18

Expense Ratio, Percent

0.35%

AssetsNet

$ 238,699,721

Holdings Count | Holding

527

Advisory Fees Paid, Amount

$ 190,088

InvestmentCompanyPortfolioTurnover

72.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets$238,699,721
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)527
Portfolio Turnover Rate72%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)$190,088

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	21.5%
Electric	3.4%
Finance Companies	3.5%
Automotive	4.3%
ABS Other	4.4%
Life Insurance	4.4%
Non-Agency Commercial Mortgage-Backed Securities	8.0%
ABS Car Loan	12.7%
Banking	13.7%
Treasuries	24.3%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	0.8
US Treasury	24.5
Not rated^{Footnote Reference^}	14.1
BBB	24.5
A	19.3
AA	6.7
AAA	10.1

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018125

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Securitized Asset Fund

Class Name

Institutional Class

Trading Symbol

LSSAX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Securitized Asset Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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
Institutional Class	$0	0.00%

Expenses Paid, Amount

$ 0

Expense Ratio, Percent

0.00%

AssetsNet

$ 1,672,859,276

Holdings Count | Holding

668

Advisory Fees Paid, Amount

$ 0

InvestmentCompanyPortfolioTurnover

44.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$1,672,859,276
# of Portfolio Holdings (including overnight repurchase agreements and derivatives)	668
Portfolio Turnover Rate	44%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$0

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	(1.2%)
Short-Term Investments	7.9%
Collateralized Loan Obligations	4.6%
ABS Home Equity	4.7%
Agency Commercial Mortgage-Backed Securities	7.0%
ABS Other	7.8%
Non-Agency Commercial Mortgage-Backed Securities	8.4%
ABS Car Loan	9.1%
Collateralized Mortgage Obligations	11.9%
Mortgage Related	39.7%

Footnote	Description
Footnote^*	Net of other assets less liabilities (including futures contracts)

Credit Quality^{Footnote Reference†}

Value	Value
Cash & equivalents	3.1
Not rated^{Footnote Reference^}	19.7
B	0.1
BB	0.3
BBB	0.7
A	2.4
AA	66.0
AAA	7.7

Footnote	Description
Footnote^†	Credit ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
Footnote^{^}	Not Rated category represents only those securities not rated by S&P Global Ratings. Such securities may be rated by other NRSROs not shown here.

Credit Quality Explanation [Text Block]

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018134

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Small Cap Value Fund

Class Name

Institutional Class

Trading Symbol

LSSCX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Small Cap Value Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Institutional Class	$44	0.90%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 44

Expense Ratio, Percent

0.90%

AssetsNet

$ 332,098,080

Holdings Count | Holding

114

Advisory Fees Paid, Amount

$ 1,343,976

InvestmentCompanyPortfolioTurnover

18.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$332,098,080
# of Portfolio Holdings (including overnight repurchase agreements)	114
Portfolio Turnover Rate	18%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$1,343,976

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	50.3%
Energy Equipment & Services	3.0%
Capital Markets	3.1%
Commercial Services & Supplies	3.2%
Oil, Gas & Consumable Fuels	3.3%
Health Care Providers & Services	3.5%
Aerospace & Defense	3.5%
Machinery	3.7%
Insurance	3.8%
Trading Companies & Distributors	3.9%
Electronic Equipment, Instruments & Components	6.3%
Banks	12.4%

Footnote	Description
Footnote^*	Net of other assets less liabilities

Top Ten Holdings

Moog, Inc., Class A	1.9%
U.S. Cellular Corp.	1.8%
Federal Agricultural Mortgage Corp., Class C	1.6%
Knife River Corp.	1.6%
Wintrust Financial Corp.	1.5%
Antero Resources Corp.	1.5%
Vontier Corp.	1.5%
Talen Energy Corp.	1.5%
Home BancShares, Inc.	1.4%
Skyward Specialty Insurance Group, Inc.	1.4%

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018135

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Small Cap Value Fund

Class Name

Retail Class

Trading Symbol

LSCRX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Small Cap Value Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Retail Class	$56	1.15%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 56

Expense Ratio, Percent

1.15%

AssetsNet

$ 332,098,080

Holdings Count | Holding

114

Advisory Fees Paid, Amount

$ 1,343,976

InvestmentCompanyPortfolioTurnover

18.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$332,098,080
# of Portfolio Holdings (including overnight repurchase agreements)	114
Portfolio Turnover Rate	18%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$1,343,976

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	50.3%
Energy Equipment & Services	3.0%
Capital Markets	3.1%
Commercial Services & Supplies	3.2%
Oil, Gas & Consumable Fuels	3.3%
Health Care Providers & Services	3.5%
Aerospace & Defense	3.5%
Machinery	3.7%
Insurance	3.8%
Trading Companies & Distributors	3.9%
Electronic Equipment, Instruments & Components	6.3%
Banks	12.4%

Footnote	Description
Footnote^*	Net of other assets less liabilities

Top Ten Holdings

Moog, Inc., Class A	1.9%
U.S. Cellular Corp.	1.8%
Federal Agricultural Mortgage Corp., Class C	1.6%
Knife River Corp.	1.6%
Wintrust Financial Corp.	1.5%
Antero Resources Corp.	1.5%
Vontier Corp.	1.5%
Talen Energy Corp.	1.5%
Home BancShares, Inc.	1.4%
Skyward Specialty Insurance Group, Inc.	1.4%

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000018136

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Small Cap Value Fund

Class Name

Admin Class

Trading Symbol

LSVAX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Small Cap Value Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Admin Class	$68	1.40%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 68

Expense Ratio, Percent

1.40%

AssetsNet

$ 332,098,080

Holdings Count | Holding

114

Advisory Fees Paid, Amount

$ 1,343,976

InvestmentCompanyPortfolioTurnover

18.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$332,098,080
# of Portfolio Holdings (including overnight repurchase agreements)	114
Portfolio Turnover Rate	18%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$1,343,976

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	50.3%
Energy Equipment & Services	3.0%
Capital Markets	3.1%
Commercial Services & Supplies	3.2%
Oil, Gas & Consumable Fuels	3.3%
Health Care Providers & Services	3.5%
Aerospace & Defense	3.5%
Machinery	3.7%
Insurance	3.8%
Trading Companies & Distributors	3.9%
Electronic Equipment, Instruments & Components	6.3%
Banks	12.4%

Footnote	Description
Footnote^*	Net of other assets less liabilities

Top Ten Holdings

Moog, Inc., Class A	1.9%
U.S. Cellular Corp.	1.8%
Federal Agricultural Mortgage Corp., Class C	1.6%
Knife River Corp.	1.6%
Wintrust Financial Corp.	1.5%
Antero Resources Corp.	1.5%
Vontier Corp.	1.5%
Talen Energy Corp.	1.5%
Home BancShares, Inc.	1.4%
Skyward Specialty Insurance Group, Inc.	1.4%

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

C000125495

Shareholder Report [Line Items]

Fund Name

Loomis Sayles Small Cap Value Fund

Class Name

Class N

Trading Symbol

LSCNX

Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about Loomis Sayles Small Cap Value Fund for the period of October 1, 2024 to March 31, 2025.

Shareholder Report Annual or Semi-Annual

Semi-annual Shareholder Report

Additional Information [Text Block]

Additional Information Phone Number

(800) 633-3330

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^{Footnote Reference†}
Class N	$41	0.85%

Footnote	Description
Footnote^†	Annualized for periods less than one year (if applicable).

Expenses Paid, Amount

$ 41

Expense Ratio, Percent

0.85%

AssetsNet

$ 332,098,080

Holdings Count | Holding

114

Advisory Fees Paid, Amount

$ 1,343,976

InvestmentCompanyPortfolioTurnover

18.00%

Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets	$332,098,080
# of Portfolio Holdings (including overnight repurchase agreements)	114
Portfolio Turnover Rate	18%
Total Advisory Fees Paid (after waiver/reimbursement, if applicable)	$1,343,976

Holdings [Text Block]

Industry Summary

Value	Value
Other investments less than 3% of net assets^{Footnote Reference*}	50.3%
Energy Equipment & Services	3.0%
Capital Markets	3.1%
Commercial Services & Supplies	3.2%
Oil, Gas & Consumable Fuels	3.3%
Health Care Providers & Services	3.5%
Aerospace & Defense	3.5%
Machinery	3.7%
Insurance	3.8%
Trading Companies & Distributors	3.9%
Electronic Equipment, Instruments & Components	6.3%
Banks	12.4%

Footnote	Description
Footnote^*	Net of other assets less liabilities

Top Ten Holdings

Moog, Inc., Class A	1.9%
U.S. Cellular Corp.	1.8%
Federal Agricultural Mortgage Corp., Class C	1.6%
Knife River Corp.	1.6%
Wintrust Financial Corp.	1.5%
Antero Resources Corp.	1.5%
Vontier Corp.	1.5%
Talen Energy Corp.	1.5%
Home BancShares, Inc.	1.4%
Skyward Specialty Insurance Group, Inc.	1.4%

Material Fund Change [Text Block]

Material Fund Changes

There were no material fund changes during the period.

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Country Weightings

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Country Weightings

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Country Weightings

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Credit QualityFootnote Reference†

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Top Ten Holdings

Material Fund Changes

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Key Fund Statistics

Industry Summary

Top Ten Holdings

Material Fund Changes

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}

Credit Quality^{Footnote Reference†}