S000006640 [Member] Expense Example - Loomis Sayles Fixed Income Fund - Institutional Class	Sep. 30, 2025 USD ($)
Prospectus [Line Items]
Expense Example, with Redemption, 1 Year	$ 63
Expense Example, with Redemption, 3 Years	199
Expense Example, with Redemption, 5 Years	346
Expense Example, with Redemption, 10 Years	$ 774

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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