S000001273 [Member] Expense Example - MID CAP INDEX FUND - MID CAP INDEX FUND	Mar. 31, 2026 USD ($)
Prospectus [Line Items]
Expense Example, with Redemption, 1 Year	$ 10
Expense Example, with Redemption, 3 Years	45
Expense Example, with Redemption, 5 Years	84
Expense Example, with Redemption, 10 Years	$ 199

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Form N-1A
-Section 3
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Form N-1A
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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