State Street SPDR Portfolio SP 400 Mid Cap ETF Average Annual Total Returns |
12 Months Ended | 28 Months Ended | 60 Months Ended | 65 Months Ended | 86 Months Ended | 96 Months Ended | 118 Months Ended | 120 Months Ended | |||
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| S&P MidCap 400 Index/S&P 1000 Index/Russell Small Cap Completeness Index (reflects no deduction for fees, expenses or taxes)[Member] | |||||||||||
| Prospectus [Line Items] | |||||||||||
| Average Annual Return, Percent | [1] | 7.50% | 9.12% | 10.40% | |||||||
| S&P 500 Index (reflects no deduction for fees, expenses or taxes)[Member] | |||||||||||
| Prospectus [Line Items] | |||||||||||
| Average Annual Return, Percent | 17.88% | 21.76% | 14.42% | 16.50% | 15.33% | 14.27% | 15.31% | 15.77% | 14.82% | ||
| State Street SPDR Portfolio SP 400 Mid Cap ETF | |||||||||||
| Prospectus [Line Items] | |||||||||||
| Average Annual Return, Percent | 7.48% | 9.08% | 10.36% | ||||||||
| State Street SPDR Portfolio SP 400 Mid Cap ETF | After Taxes on Distributions | |||||||||||
| Prospectus [Line Items] | |||||||||||
| Average Annual Return, Percent | 7.02% | 8.62% | 9.81% | ||||||||
| State Street SPDR Portfolio SP 400 Mid Cap ETF | After Taxes on Distributions and Sales | |||||||||||
| Prospectus [Line Items] | |||||||||||
| Average Annual Return, Percent | 4.58% | 7.05% | 8.33% | ||||||||
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