S000001273 [Member] Average Annual Total Returns |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| Russell 3000® Index (reflects no deduction for fees, expenses, or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 17.15% | 13.15% | 14.29% |
| S&P MidCap 400® Index (reflects no deduction for fees, expenses, or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.50% | 9.12% | 10.72% |
| MID CAP INDEX FUND | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.42% | 9.00% | 10.58% |
| MID CAP INDEX FUND | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.61% | 6.66% | 8.58% |
| MID CAP INDEX FUND | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.42% | 6.67% | 8.16% |