| Form N-CSR Cover | 12 Months Ended |
| Oct. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | EATON VANCE SPECIAL INVESTMENT TRUST |
| Entity Central Index Key | 0000031266 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Oct. 31, 2024 |
| Shareholder Report | 12 Months Ended |
| Oct. 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | EATON VANCE SPECIAL INVESTMENT TRUST |
| Entity Central Index Key | 0000031266 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Oct. 31, 2024 |
| C000086684 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance Short Duration Inflation-Protected Income Fund |
| Class Name | Class A |
| Trading Symbol | EARRX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Eaton Vance Short Duration Inflation-Protected Income Fund for the period of November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B19"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last year? Footnote Reference (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 Class A $114 1.10% Footnote Description Footnote * Expenses in the table reflect the expenses of both the Fund and Short Duration Inflation-Protected Income Portfolio and Senior Debt Portfolio, the Portfolios in which it invests. |
| Expenses Paid, Amount | $ 114 |
| Expense Ratio, Percent | 1.10% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? Key contributors to (↑) and detractors from (↓) performance, relative to the ICE BofA 1-5 Year U.S. Inflation-Linked Treasury Index (the Index): ↑ The Treasury Inflation-Protected Securities (TIPS) held by the Fund outperformed the TIPS represented within the Index due to favorable security selections, benefiting Index-relative performance during the period ↑ Out-of-Index allocations to floating-rate bank loans (FRBL) and commercial mortgage-backed securities (CMBS) contributed to Index-relative returns, as both FRBL and CMBS generally outperformed TIPS given their higher yields and the underlying strength of the U.S. economy and corporate earnings ↑ The Fund’s strategy of swapping nominal interest payments for payments based on changes in the Consumer Price Index ― and other measures of inflation ― helped performance during the period ↓ Management’s decision to maintain the Fund’s out-of-Index allocation to FRBL at the lower end of the targeted range detracted from Index-relative returns ↓ The Fund’s allocation to cash ― while minimal ― detracted from Index-relative returns due to the outperformance of riskier asset classes during the period |
| Performance Past Does Not Indicate Future [Text] | THE FUND'S PAST PERFORMANCE IS NO GUARANTEE OF FUTURE RESULTS. |
| Line Graph [Table Text Block] | Class A with Maximum Sales Charge Bloomberg U.S. Universal Index ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 10/14 $10,000 $10,000 $10,000 11/14 $9,655 $10,054 $9,981 12/14 $9,484 $10,036 $9,838 1/15 $9,563 $10,227 $9,946 2/15 $9,602 $10,167 $9,917 3/15 $9,544 $10,209 $9,883 4/15 $9,631 $10,197 $9,957 5/15 $9,612 $10,180 $9,951 6/15 $9,595 $10,066 $9,947 7/15 $9,551 $10,125 $9,912 8/15 $9,499 $10,095 $9,887 9/15 $9,465 $10,134 $9,874 10/15 $9,476 $10,167 $9,874 11/15 $9,438 $10,130 $9,853 12/15 $9,380 $10,079 $9,824 1/16 $9,400 $10,190 $9,896 2/16 $9,400 $10,263 $9,922 3/16 $9,601 $10,388 $10,038 4/16 $9,637 $10,459 $10,040 5/16 $9,640 $10,467 $10,022 6/16 $9,685 $10,652 $10,136 7/16 $9,717 $10,739 $10,125 8/16 $9,727 $10,751 $10,087 9/16 $9,835 $10,753 $10,163 10/16 $9,871 $10,682 $10,166 11/16 $9,859 $10,442 $10,104 12/16 $9,924 $10,473 $10,134 1/17 $9,985 $10,510 $10,186 2/17 $10,002 $10,591 $10,197 3/17 $10,018 $10,588 $10,214 4/17 $10,014 $10,675 $10,214 5/17 $10,012 $10,758 $10,207 6/17 $9,967 $10,749 $10,155 7/17 $10,008 $10,802 $10,189 8/17 $10,039 $10,895 $10,222 9/17 $10,041 $10,857 $10,204 10/17 $10,072 $10,870 $10,221 11/17 $10,072 $10,854 $10,200 12/17 $10,103 $10,901 $10,217 1/18 $10,103 $10,797 $10,180 2/18 $10,103 $10,694 $10,171 3/18 $10,140 $10,748 $10,232 4/18 $10,140 $10,676 $10,224 5/18 $10,161 $10,735 $10,265 6/18 $10,186 $10,719 $10,279 7/18 $10,197 $10,741 $10,258 8/18 $10,249 $10,794 $10,314 9/18 $10,249 $10,748 $10,281 10/18 $10,186 $10,658 $10,236 11/18 $10,144 $10,706 $10,240 12/18 $10,053 $10,874 $10,258 1/19 $10,201 $11,024 $10,341 2/19 $10,243 $11,036 $10,353 3/19 $10,284 $11,235 $10,440 4/19 $10,379 $11,251 $10,491 5/19 $10,379 $11,423 $10,556 6/19 $10,432 $11,585 $10,628 7/19 $10,453 $11,619 $10,626 8/19 $10,432 $11,882 $10,691 9/19 $10,432 $11,830 $10,654 10/19 $10,432 $11,869 $10,686 11/19 $10,464 $11,866 $10,694 12/19 $10,584 $11,884 $10,779 1/20 $10,606 $12,097 $10,836 2/20 $10,573 $12,278 $10,899 3/20 $9,861 $12,039 $10,707 4/20 $10,100 $12,280 $10,846 5/20 $10,307 $12,394 $10,925 6/20 $10,466 $12,498 $11,015 7/20 $10,607 $12,717 $11,111 8/20 $10,792 $12,644 $11,259 9/20 $10,792 $12,621 $11,232 10/20 $10,792 $12,576 $11,202 11/20 $10,946 $12,740 $11,274 12/20 $11,118 $12,784 $11,392 1/21 $11,239 $12,704 $11,462 2/21 $11,283 $12,540 $11,447 3/21 $11,346 $12,394 $11,523 4/21 $11,457 $12,498 $11,631 5/21 $11,568 $12,546 $11,730 6/21 $11,585 $12,637 $11,723 7/21 $11,731 $12,764 $11,899 8/21 $11,764 $12,756 $11,901 9/21 $11,794 $12,647 $11,888 10/21 $11,896 $12,636 $11,966 11/21 $11,896 $12,652 $11,996 12/21 $11,951 $12,643 $12,020 1/22 $11,905 $12,366 $11,930 2/22 $12,031 $12,197 $12,068 3/22 $11,994 $11,870 $11,985 4/22 $12,017 $11,427 $11,950 5/22 $11,914 $11,490 $11,985 6/22 $11,611 $11,261 $11,773 7/22 $11,926 $11,544 $11,997 8/22 $11,833 $11,244 $11,846 9/22 $11,371 $10,759 $11,394 10/22 $11,537 $10,641 $11,509 11/22 $11,609 $11,038 $11,568 12/22 $11,568 $11,001 $11,541 1/23 $11,711 $11,342 $11,622 2/23 $11,723 $11,063 $11,554 3/23 $11,865 $11,323 $11,798 4/23 $11,901 $11,392 $11,830 5/23 $11,805 $11,274 $11,727 6/23 $11,840 $11,256 $11,689 7/23 $11,925 $11,267 $11,748 8/23 $11,962 $11,200 $11,753 9/23 $11,961 $10,932 $11,719 10/23 $11,986 $10,768 $11,761 11/23 $12,121 $11,253 $11,898 12/23 $12,257 $11,680 $12,040 1/24 $12,332 $11,652 $12,094 2/24 $12,332 $11,512 $12,047 3/24 $12,418 $11,625 $12,119 4/24 $12,431 $11,353 $12,090 5/24 $12,544 $11,542 $12,217 6/24 $12,606 $11,647 $12,297 7/24 $12,708 $11,911 $12,428 8/24 $12,772 $12,087 $12,503 9/24 $12,888 $12,253 $12,639 10/24 $12,858 $11,974 $12,556 |
| Average Annual Return [Table Text Block] | Fund 1 Year 5 Years 10 Years Class A 7.32% 4.27% 2.89% Class A with 3.25% Maximum Sales Charge 3.79% 3.58% 2.54% Bloomberg U.S. Universal Index Footnote Reference 11.20% 0.18% 1.82% ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 6.76% 3.27% 2.30% |
| AssetsNet | $ 435,059,165 |
| Holdings Count | Holding | 722 |
| Advisory Fees Paid, Amount | $ 1,555,560 |
| InvestmentCompanyPortfolioTurnover | 6% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $435,059,165 # of Portfolio Holdings (for Short Duration Inflation-Protected Income and Senior Debt Portfolios) 722 Portfolio Turnover Rate 6% Total Advisory Fees Paid $1,555,560 |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| C000086685 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance Short Duration Inflation-Protected Income Fund |
| Class Name | Class C |
| Trading Symbol | ECRRX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Eaton Vance Short Duration Inflation-Protected Income Fund for the period of November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B43"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last year? Footnote Reference (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 Class C $190 1.84% Footnote Description Footnote * Expenses in the table reflect the expenses of both the Fund and Short Duration Inflation-Protected Income Portfolio and Senior Debt Portfolio, the Portfolios in which it invests. |
| Expenses Paid, Amount | $ 190 |
| Expense Ratio, Percent | 1.84% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? Key contributors to (↑) and detractors from (↓) performance, relative to the ICE BofA 1-5 Year U.S. Inflation-Linked Treasury Index (the Index): ↓ Management’s decision to maintain the Fund’s out-of-Index allocation to floating-rate bank loans (FRBL) at the lower end of the targeted range detracted from Index-relative returns ↓ The Fund’s allocation to cash ― while minimal ― detracted from Index-relative returns due to the outperformance of riskier asset classes during the period ↑ The Treasury Inflation-Protected Securities (TIPS) held by the Fund outperformed the TIPS represented within the Index due to favorable security selections, benefiting Index-relative performance during the period ↑ Out-of-Index allocations to FRBL and commercial mortgage-backed securities (CMBS) contributed to Index-relative returns, as both FRBL and CMBS generally outperformed TIPS given their higher yields and the underlying strength of the U.S. economy and corporate earnings ↑ The Fund’s strategy of swapping nominal interest payments for payments based on changes in the Consumer Price Index ― and other measures of inflation ― helped performance during the period |
| Performance Past Does Not Indicate Future [Text] | THE FUND'S PAST PERFORMANCE IS NO GUARANTEE OF FUTURE RESULTS. |
| Line Graph [Table Text Block] | Class C Bloomberg U.S. Universal Index ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 10/14 $10,000 $10,000 $10,000 11/14 $9,963 $10,054 $9,981 12/14 $9,777 $10,036 $9,838 1/15 $9,858 $10,227 $9,946 2/15 $9,888 $10,167 $9,917 3/15 $9,828 $10,209 $9,883 4/15 $9,908 $10,197 $9,957 5/15 $9,878 $10,180 $9,951 6/15 $9,863 $10,066 $9,947 7/15 $9,812 $10,125 $9,912 8/15 $9,752 $10,095 $9,887 9/15 $9,701 $10,134 $9,874 10/15 $9,716 $10,167 $9,874 11/15 $9,670 $10,130 $9,853 12/15 $9,605 $10,079 $9,824 1/16 $9,615 $10,190 $9,896 2/16 $9,605 $10,263 $9,922 3/16 $9,808 $10,388 $10,038 4/16 $9,835 $10,459 $10,040 5/16 $9,841 $10,467 $10,022 6/16 $9,883 $10,652 $10,136 7/16 $9,909 $10,739 $10,125 8/16 $9,913 $10,751 $10,087 9/16 $10,008 $10,753 $10,163 10/16 $10,049 $10,682 $10,166 11/16 $10,020 $10,442 $10,104 12/16 $10,080 $10,473 $10,134 1/17 $10,131 $10,510 $10,186 2/17 $10,142 $10,591 $10,197 3/17 $10,157 $10,588 $10,214 4/17 $10,149 $10,675 $10,214 5/17 $10,141 $10,758 $10,207 6/17 $10,088 $10,749 $10,155 7/17 $10,120 $10,802 $10,189 8/17 $10,140 $10,895 $10,222 9/17 $10,145 $10,857 $10,204 10/17 $10,176 $10,870 $10,221 11/17 $10,155 $10,854 $10,200 12/17 $10,186 $10,901 $10,217 1/18 $10,176 $10,797 $10,180 2/18 $10,176 $10,694 $10,171 3/18 $10,206 $10,748 $10,232 4/18 $10,206 $10,676 $10,224 5/18 $10,217 $10,735 $10,265 6/18 $10,236 $10,719 $10,279 7/18 $10,236 $10,741 $10,258 8/18 $10,278 $10,794 $10,314 9/18 $10,270 $10,748 $10,281 10/18 $10,207 $10,658 $10,236 11/18 $10,164 $10,706 $10,240 12/18 $10,063 $10,874 $10,258 1/19 $10,201 $11,024 $10,341 2/19 $10,243 $11,036 $10,353 3/19 $10,274 $11,235 $10,440 4/19 $10,359 $11,251 $10,491 5/19 $10,359 $11,423 $10,556 6/19 $10,401 $11,585 $10,628 7/19 $10,422 $11,619 $10,626 8/19 $10,390 $11,882 $10,691 9/19 $10,378 $11,830 $10,654 10/19 $10,368 $11,869 $10,686 11/19 $10,400 $11,866 $10,694 12/19 $10,520 $11,884 $10,779 1/20 $10,531 $12,097 $10,836 2/20 $10,487 $12,278 $10,899 3/20 $9,775 $12,039 $10,707 4/20 $10,003 $12,280 $10,846 5/20 $10,209 $12,394 $10,925 6/20 $10,346 $12,498 $11,015 7/20 $10,488 $12,717 $11,111 8/20 $10,673 $12,644 $11,259 9/20 $10,663 $12,621 $11,232 10/20 $10,652 $12,576 $11,202 11/20 $10,804 $12,740 $11,274 12/20 $10,962 $12,784 $11,392 1/21 $11,083 $12,704 $11,462 2/21 $11,116 $12,540 $11,447 3/21 $11,159 $12,394 $11,523 4/21 $11,269 $12,498 $11,631 5/21 $11,368 $12,546 $11,730 6/21 $11,379 $12,637 $11,723 7/21 $11,524 $12,764 $11,899 8/21 $11,546 $12,756 $11,901 9/21 $11,569 $12,647 $11,888 10/21 $11,659 $12,636 $11,966 11/21 $11,648 $12,652 $11,996 12/21 $11,694 $12,643 $12,020 1/22 $11,638 $12,366 $11,930 2/22 $11,762 $12,197 $12,068 3/22 $11,720 $11,870 $11,985 4/22 $11,731 $11,427 $11,950 5/22 $11,618 $11,490 $11,985 6/22 $11,323 $11,261 $11,773 7/22 $11,622 $11,544 $11,997 8/22 $11,518 $11,244 $11,846 9/22 $11,066 $10,759 $11,394 10/22 $11,218 $10,641 $11,509 11/22 $11,288 $11,038 $11,568 12/22 $11,228 $11,001 $11,541 1/23 $11,369 $11,342 $11,622 2/23 $11,369 $11,063 $11,554 3/23 $11,499 $11,323 $11,798 4/23 $11,522 $11,392 $11,830 5/23 $11,428 $11,274 $11,727 6/23 $11,451 $11,256 $11,689 7/23 $11,534 $11,267 $11,748 8/23 $11,558 $11,200 $11,753 9/23 $11,547 $10,932 $11,719 10/23 $11,571 $10,768 $11,761 11/23 $11,692 $11,253 $11,898 12/23 $11,826 $11,680 $12,040 1/24 $11,874 $11,652 $12,094 2/24 $11,874 $11,512 $12,047 3/24 $11,948 $11,625 $12,119 4/24 $11,948 $11,353 $12,090 5/24 $12,058 $11,542 $12,217 6/24 $12,108 $11,647 $12,297 7/24 $12,195 $11,911 $12,428 8/24 $12,245 $12,087 $12,503 9/24 $12,359 $12,253 $12,639 10/24 $12,507 $11,974 $12,556 |
| Average Annual Return [Table Text Block] | Fund 1 Year 5 Years 10 Years Class C, with conversion to Class A after 8 years 6.49% 3.51% 2.26% Class C, with 1% Maximum Deferred Sales Charge and conversion to Class A after 8 years 5.49% 3.51% 2.26% Bloomberg U.S. Universal Index Footnote Reference 11.20% 0.18% 1.82% ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 6.76% 3.27% 2.30% |
| AssetsNet | $ 435,059,165 |
| Holdings Count | Holding | 722 |
| Advisory Fees Paid, Amount | $ 1,555,560 |
| InvestmentCompanyPortfolioTurnover | 6% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $435,059,165 # of Portfolio Holdings (for Short Duration Inflation-Protected Income and Senior Debt Portfolios) 722 Portfolio Turnover Rate 6% Total Advisory Fees Paid $1,555,560 |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| C000086686 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance Short Duration Inflation-Protected Income Fund |
| Class Name | Class I |
| Trading Symbol | EIRRX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Eaton Vance Short Duration Inflation-Protected Income Fund for the period of November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B67"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last year? Footnote Reference (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 Class I $88 0.85% Footnote Description Footnote * Expenses in the table reflect the expenses of both the Fund and Short Duration Inflation-Protected Income Portfolio and Senior Debt Portfolio, the Portfolios in which it invests. |
| Expenses Paid, Amount | $ 88 |
| Expense Ratio, Percent | 0.85% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? Key contributors to (↑) and detractors from (↓) performance, relative to the ICE BofA 1-5 Year U.S. Inflation-Linked Treasury Index (the Index): ↑ The Treasury Inflation-Protected Securities (TIPS) held by the Fund outperformed the TIPS represented within the Index due to favorable security selections, benefiting Index-relative performance during the period ↑ Out-of-Index allocations to floating-rate bank loans (FRBL) and commercial mortgage-backed securities (CMBS) contributed to Index-relative returns, as both FRBL and CMBS generally outperformed TIPS given their higher yields and the underlying strength of the U.S. economy and corporate earnings ↑ The Fund’s strategy of swapping nominal interest payments for payments based on changes in the Consumer Price Index ― and other measures of inflation ― helped performance during the period ↓ Management’s decision to maintain the Fund’s out-of-Index allocation to FRBL at the lower end of the targeted range detracted from Index-relative returns ↓ The Fund’s allocation to cash ― while minimal ― detracted from Index-relative returns due to the outperformance of riskier asset classes during the period |
| Performance Past Does Not Indicate Future [Text] | THE FUND'S PAST PERFORMANCE IS NO GUARANTEE OF FUTURE RESULTS. |
| Line Graph [Table Text Block] | Class I Bloomberg U.S. Universal Index ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 10/14 $1,000,000 $1,000,000 $1,000,000 11/14 $998,108 $1,005,397 $998,068 12/14 $979,791 $1,003,580 $983,836 1/15 $987,973 $1,022,684 $994,624 2/15 $991,994 $1,016,723 $991,728 3/15 $986,968 $1,020,920 $988,261 4/15 $996,014 $1,019,735 $995,721 5/15 $994,002 $1,017,951 $995,120 6/15 $992,484 $1,006,590 $994,729 7/15 $988,167 $1,012,452 $991,180 8/15 $983,024 $1,009,468 $988,652 9/15 $979,686 $1,013,420 $987,374 10/15 $981,007 $1,016,659 $987,420 11/15 $977,855 $1,012,952 $985,284 12/15 $972,041 $1,007,891 $982,388 1/16 $973,313 $1,019,017 $989,615 2/16 $974,338 $1,026,256 $992,248 3/16 $994,618 $1,038,833 $1,003,765 4/16 $998,517 $1,045,911 $1,004,040 5/16 $1,000,037 $1,046,728 $1,002,242 6/16 $1,004,996 $1,065,155 $1,013,642 7/16 $1,008,523 $1,073,933 $1,012,469 8/16 $1,009,777 $1,075,091 $1,008,704 9/16 $1,021,224 $1,075,347 $1,016,287 10/16 $1,025,133 $1,068,213 $1,016,619 11/16 $1,023,049 $1,044,202 $1,010,420 12/16 $1,031,019 $1,047,304 $1,013,403 1/17 $1,036,433 $1,050,999 $1,018,616 2/17 $1,038,552 $1,059,108 $1,019,737 3/17 $1,040,427 $1,058,753 $1,021,383 4/17 $1,041,218 $1,067,538 $1,021,424 5/17 $1,041,218 $1,075,775 $1,020,741 6/17 $1,036,732 $1,074,863 $1,015,545 7/17 $1,041,008 $1,080,216 $1,018,925 8/17 $1,044,188 $1,089,536 $1,022,200 9/17 $1,045,019 $1,085,702 $1,020,396 10/17 $1,048,212 $1,087,005 $1,022,095 11/17 $1,048,213 $1,085,360 $1,020,023 12/17 $1,050,951 $1,090,145 $1,021,715 1/18 $1,052,024 $1,079,655 $1,017,968 2/18 $1,053,095 $1,069,417 $1,017,145 3/18 $1,056,558 $1,074,811 $1,023,216 4/18 $1,056,560 $1,067,639 $1,022,433 5/18 $1,059,794 $1,073,462 $1,026,467 6/18 $1,061,944 $1,071,905 $1,027,915 7/18 $1,063,025 $1,074,148 $1,025,819 8/18 $1,068,454 $1,079,440 $1,031,365 9/18 $1,068,089 $1,074,815 $1,028,055 10/18 $1,062,617 $1,065,824 $1,023,642 11/18 $1,059,338 $1,070,617 $1,024,045 12/18 $1,049,333 $1,087,367 $1,025,819 1/19 $1,064,764 $1,102,360 $1,034,126 2/19 $1,070,279 $1,103,561 $1,035,323 3/19 $1,074,570 $1,123,489 $1,043,980 4/19 $1,083,392 $1,125,062 $1,049,064 5/19 $1,084,495 $1,142,296 $1,055,631 6/19 $1,089,559 $1,158,453 $1,062,829 7/19 $1,092,897 $1,161,901 $1,062,566 8/19 $1,090,671 $1,188,192 $1,069,063 9/19 $1,091,436 $1,183,044 $1,065,374 10/19 $1,091,437 $1,186,867 $1,068,620 11/19 $1,094,803 $1,186,629 $1,069,413 12/19 $1,108,114 $1,188,398 $1,077,878 1/20 $1,110,378 $1,209,727 $1,083,616 2/20 $1,106,984 $1,227,840 $1,089,880 3/20 $1,033,101 $1,203,856 $1,070,727 4/20 $1,058,164 $1,227,971 $1,084,585 5/20 $1,079,810 $1,239,440 $1,092,524 6/20 $1,096,483 $1,249,782 $1,101,549 7/20 $1,111,312 $1,271,736 $1,111,075 8/20 $1,131,846 $1,264,402 $1,125,914 9/20 $1,131,390 $1,262,124 $1,123,235 10/20 $1,131,392 $1,257,613 $1,120,199 11/20 $1,148,623 $1,274,024 $1,127,350 12/20 $1,166,183 $1,278,423 $1,139,171 1/21 $1,180,081 $1,270,388 $1,146,246 2/21 $1,184,708 $1,253,996 $1,144,658 3/21 $1,190,783 $1,239,403 $1,152,265 4/21 $1,203,572 $1,249,825 $1,163,093 5/21 $1,214,033 $1,254,592 $1,173,040 6/21 $1,216,546 $1,263,738 $1,172,276 7/21 $1,233,020 $1,276,427 $1,189,905 8/21 $1,236,550 $1,275,575 $1,190,051 9/21 $1,240,444 $1,264,683 $1,188,766 10/21 $1,251,169 $1,263,649 $1,196,635 11/21 $1,251,169 $1,265,175 $1,199,636 12/21 $1,257,603 $1,264,322 $1,201,982 1/22 $1,251,603 $1,236,603 $1,192,987 2/22 $1,266,003 $1,219,743 $1,206,833 3/22 $1,262,857 $1,187,019 $1,198,462 4/22 $1,265,276 $1,142,746 $1,195,018 5/22 $1,254,389 $1,149,034 $1,198,451 6/22 $1,223,246 $1,126,073 $1,177,296 7/22 $1,256,406 $1,154,385 $1,199,700 8/22 $1,246,581 $1,124,375 $1,184,622 9/22 $1,198,773 $1,075,933 $1,139,405 10/22 $1,216,292 $1,064,128 $1,150,928 11/22 $1,223,800 $1,103,805 $1,156,789 12/22 $1,219,048 $1,100,056 $1,154,068 1/23 $1,235,436 $1,134,180 $1,162,200 2/23 $1,236,697 $1,106,311 $1,155,382 3/23 $1,252,434 $1,132,265 $1,179,823 4/23 $1,256,241 $1,139,182 $1,182,970 5/23 $1,246,089 $1,127,371 $1,172,672 6/23 $1,250,556 $1,125,619 $1,168,855 7/23 $1,259,571 $1,126,738 $1,174,809 8/23 $1,263,435 $1,119,953 $1,175,329 9/23 $1,264,208 $1,093,247 $1,171,873 10/23 $1,266,811 $1,076,807 $1,176,105 11/23 $1,281,133 $1,125,268 $1,189,765 12/23 $1,296,305 $1,167,966 $1,203,967 1/24 $1,302,898 $1,165,171 $1,209,402 2/24 $1,304,217 $1,151,201 $1,204,668 3/24 $1,312,855 $1,162,504 $1,211,865 4/24 $1,315,510 $1,135,338 $1,209,028 5/24 $1,328,784 $1,154,158 $1,221,748 6/24 $1,334,822 $1,164,708 $1,229,705 7/24 $1,345,642 $1,191,145 $1,242,775 8/24 $1,352,404 $1,208,679 $1,250,264 9/24 $1,365,591 $1,225,257 $1,263,941 10/24 $1,362,884 $1,197,428 $1,255,640 |
| Average Annual Return [Table Text Block] | Fund 1 Year 5 Years 10 Years Class I 7.58% 4.54% 3.14% Bloomberg U.S. Universal Index Footnote Reference 11.20% 0.18% 1.82% ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index 6.76% 3.27% 2.30% |
| AssetsNet | $ 435,059,165 |
| Holdings Count | Holding | 722 |
| Advisory Fees Paid, Amount | $ 1,555,560 |
| InvestmentCompanyPortfolioTurnover | 6% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $435,059,165 # of Portfolio Holdings (for Short Duration Inflation-Protected Income and Senior Debt Portfolios) 722 Portfolio Turnover Rate 6% Total Advisory Fees Paid $1,555,560 |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Oct. 31, 2024 | Sep. 30, 2024 | Aug. 31, 2024 | Jul. 31, 2024 | Jun. 30, 2024 | May 31, 2024 | Apr. 30, 2024 | Mar. 31, 2024 | Feb. 29, 2024 | Jan. 31, 2024 | Dec. 31, 2023 | Nov. 30, 2023 | Oct. 31, 2023 | Sep. 30, 2023 | Aug. 31, 2023 | Jul. 31, 2023 | Jun. 30, 2023 | May 31, 2023 | Apr. 30, 2023 | Mar. 31, 2023 | Feb. 28, 2023 | Jan. 31, 2023 | Dec. 31, 2022 | Nov. 30, 2022 | Oct. 31, 2022 | Sep. 30, 2022 | Aug. 31, 2022 | Jul. 31, 2022 | Jun. 30, 2022 | May 31, 2022 | Apr. 30, 2022 | Mar. 31, 2022 | Feb. 28, 2022 | Jan. 31, 2022 | Dec. 31, 2021 | Nov. 30, 2021 | Oct. 31, 2021 | Sep. 30, 2021 | Aug. 31, 2021 | Jul. 31, 2021 | Jun. 30, 2021 | May 31, 2021 | Apr. 30, 2021 | Mar. 31, 2021 | Feb. 28, 2021 | Jan. 31, 2021 | Dec. 31, 2020 | Nov. 30, 2020 | Oct. 31, 2020 | Sep. 30, 2020 | Aug. 31, 2020 | Jul. 31, 2020 | Jun. 30, 2020 | May 31, 2020 | Apr. 30, 2020 | Mar. 31, 2020 | Feb. 29, 2020 | Jan. 31, 2020 | Dec. 31, 2019 | Nov. 30, 2019 | Oct. 31, 2019 | Sep. 30, 2019 | Aug. 31, 2019 | Jul. 31, 2019 | Jun. 30, 2019 | May 31, 2019 | Apr. 30, 2019 | Mar. 31, 2019 | Feb. 28, 2019 | Jan. 31, 2019 | Dec. 31, 2018 | Nov. 30, 2018 | Oct. 31, 2018 | Sep. 30, 2018 | Aug. 31, 2018 | Jul. 31, 2018 | Jun. 30, 2018 | May 31, 2018 | Apr. 30, 2018 | Mar. 31, 2018 | Feb. 28, 2018 | Jan. 31, 2018 | Dec. 31, 2017 | Nov. 30, 2017 | Oct. 31, 2017 | Sep. 30, 2017 | Aug. 31, 2017 | Jul. 31, 2017 | Jun. 30, 2017 | May 31, 2017 | Apr. 30, 2017 | Mar. 31, 2017 | Feb. 28, 2017 | Jan. 31, 2017 | Dec. 31, 2016 | Nov. 30, 2016 | Oct. 31, 2016 | Sep. 30, 2016 | Aug. 31, 2016 | Jul. 31, 2016 | Jun. 30, 2016 | May 31, 2016 | Apr. 30, 2016 | Mar. 31, 2016 | Feb. 29, 2016 | Jan. 31, 2016 | Dec. 31, 2015 | Nov. 30, 2015 | Oct. 31, 2015 | Sep. 30, 2015 | Aug. 31, 2015 | Jul. 31, 2015 | Jun. 30, 2015 | May 31, 2015 | Apr. 30, 2015 | Mar. 31, 2015 | Feb. 28, 2015 | Jan. 31, 2015 | Dec. 31, 2014 | Nov. 30, 2014 | Oct. 31, 2014 | |
| C000086684 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Class A with Maximum Sales Charge | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 12,858 | $ 12,888 | $ 12,772 | $ 12,708 | $ 12,606 | $ 12,544 | $ 12,431 | $ 12,418 | $ 12,332 | $ 12,332 | $ 12,257 | $ 12,121 | $ 11,986 | $ 11,961 | $ 11,962 | $ 11,925 | $ 11,840 | $ 11,805 | $ 11,901 | $ 11,865 | $ 11,723 | $ 11,711 | $ 11,568 | $ 11,609 | $ 11,537 | $ 11,371 | $ 11,833 | $ 11,926 | $ 11,611 | $ 11,914 | $ 12,017 | $ 11,994 | $ 12,031 | $ 11,905 | $ 11,951 | $ 11,896 | $ 11,896 | $ 11,794 | $ 11,764 | $ 11,731 | $ 11,585 | $ 11,568 | $ 11,457 | $ 11,346 | $ 11,283 | $ 11,239 | $ 11,118 | $ 10,946 | $ 10,792 | $ 10,792 | $ 10,792 | $ 10,607 | $ 10,466 | $ 10,307 | $ 10,100 | $ 9,861 | $ 10,573 | $ 10,606 | $ 10,584 | $ 10,464 | $ 10,432 | $ 10,432 | $ 10,432 | $ 10,453 | $ 10,432 | $ 10,379 | $ 10,379 | $ 10,284 | $ 10,243 | $ 10,201 | $ 10,053 | $ 10,144 | $ 10,186 | $ 10,249 | $ 10,249 | $ 10,197 | $ 10,186 | $ 10,161 | $ 10,140 | $ 10,140 | $ 10,103 | $ 10,103 | $ 10,103 | $ 10,072 | $ 10,072 | $ 10,041 | $ 10,039 | $ 10,008 | $ 9,967 | $ 10,012 | $ 10,014 | $ 10,018 | $ 10,002 | $ 9,985 | $ 9,924 | $ 9,859 | $ 9,871 | $ 9,835 | $ 9,727 | $ 9,717 | $ 9,685 | $ 9,640 | $ 9,637 | $ 9,601 | $ 9,400 | $ 9,400 | $ 9,380 | $ 9,438 | $ 9,476 | $ 9,465 | $ 9,499 | $ 9,551 | $ 9,595 | $ 9,612 | $ 9,631 | $ 9,544 | $ 9,602 | $ 9,563 | $ 9,484 | $ 9,655 | $ 10,000 |
| C000086685 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Class C | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 12,507 | 12,359 | 12,245 | 12,195 | 12,108 | 12,058 | 11,948 | 11,948 | 11,874 | 11,874 | 11,826 | 11,692 | 11,571 | 11,547 | 11,558 | 11,534 | 11,451 | 11,428 | 11,522 | 11,499 | 11,369 | 11,369 | 11,228 | 11,288 | 11,218 | 11,066 | 11,518 | 11,622 | 11,323 | 11,618 | 11,731 | 11,720 | 11,762 | 11,638 | 11,694 | 11,648 | 11,659 | 11,569 | 11,546 | 11,524 | 11,379 | 11,368 | 11,269 | 11,159 | 11,116 | 11,083 | 10,962 | 10,804 | 10,652 | 10,663 | 10,673 | 10,488 | 10,346 | 10,209 | 10,003 | 9,775 | 10,487 | 10,531 | 10,520 | 10,400 | 10,368 | 10,378 | 10,390 | 10,422 | 10,401 | 10,359 | 10,359 | 10,274 | 10,243 | 10,201 | 10,063 | 10,164 | 10,207 | 10,270 | 10,278 | 10,236 | 10,236 | 10,217 | 10,206 | 10,206 | 10,176 | 10,176 | 10,186 | 10,155 | 10,176 | 10,145 | 10,140 | 10,120 | 10,088 | 10,141 | 10,149 | 10,157 | 10,142 | 10,131 | 10,080 | 10,020 | 10,049 | 10,008 | 9,913 | 9,909 | 9,883 | 9,841 | 9,835 | 9,808 | 9,605 | 9,615 | 9,605 | 9,670 | 9,716 | 9,701 | 9,752 | 9,812 | 9,863 | 9,878 | 9,908 | 9,828 | 9,888 | 9,858 | 9,777 | 9,963 | 10,000 |
| C000086686 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Class I | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 1,362,884 | 1,365,591 | 1,352,404 | 1,345,642 | 1,334,822 | 1,328,784 | 1,315,510 | 1,312,855 | 1,304,217 | 1,302,898 | 1,296,305 | 1,281,133 | 1,266,811 | 1,264,208 | 1,263,435 | 1,259,571 | 1,250,556 | 1,246,089 | 1,256,241 | 1,252,434 | 1,236,697 | 1,235,436 | 1,219,048 | 1,223,800 | 1,216,292 | 1,198,773 | 1,246,581 | 1,256,406 | 1,223,246 | 1,254,389 | 1,265,276 | 1,262,857 | 1,266,003 | 1,251,603 | 1,257,603 | 1,251,169 | 1,251,169 | 1,240,444 | 1,236,550 | 1,233,020 | 1,216,546 | 1,214,033 | 1,203,572 | 1,190,783 | 1,184,708 | 1,180,081 | 1,166,183 | 1,148,623 | 1,131,392 | 1,131,390 | 1,131,846 | 1,111,312 | 1,096,483 | 1,079,810 | 1,058,164 | 1,033,101 | 1,106,984 | 1,110,378 | 1,108,114 | 1,094,803 | 1,091,437 | 1,091,436 | 1,090,671 | 1,092,897 | 1,089,559 | 1,084,495 | 1,083,392 | 1,074,570 | 1,070,279 | 1,064,764 | 1,049,333 | 1,059,338 | 1,062,617 | 1,068,089 | 1,068,454 | 1,063,025 | 1,061,944 | 1,059,794 | 1,056,560 | 1,056,558 | 1,053,095 | 1,052,024 | 1,050,951 | 1,048,213 | 1,048,212 | 1,045,019 | 1,044,188 | 1,041,008 | 1,036,732 | 1,041,218 | 1,041,218 | 1,040,427 | 1,038,552 | 1,036,433 | 1,031,019 | 1,023,049 | 1,025,133 | 1,021,224 | 1,009,777 | 1,008,523 | 1,004,996 | 1,000,037 | 998,517 | 994,618 | 974,338 | 973,313 | 972,041 | 977,855 | 981,007 | 979,686 | 983,024 | 988,167 | 992,484 | 994,002 | 996,014 | 986,968 | 991,994 | 987,973 | 979,791 | 998,108 | 1,000,000 |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 11,974 | 12,253 | 12,087 | 11,911 | 11,647 | 11,542 | 11,353 | 11,625 | 11,512 | 11,652 | 11,680 | 11,253 | 10,768 | 10,932 | 11,200 | 11,267 | 11,256 | 11,274 | 11,392 | 11,323 | 11,063 | 11,342 | 11,001 | 11,038 | 10,641 | 10,759 | 11,244 | 11,544 | 11,261 | 11,490 | 11,427 | 11,870 | 12,197 | 12,366 | 12,643 | 12,652 | 12,636 | 12,647 | 12,756 | 12,764 | 12,637 | 12,546 | 12,498 | 12,394 | 12,540 | 12,704 | 12,784 | 12,740 | 12,576 | 12,621 | 12,644 | 12,717 | 12,498 | 12,394 | 12,280 | 12,039 | 12,278 | 12,097 | 11,884 | 11,866 | 11,869 | 11,830 | 11,882 | 11,619 | 11,585 | 11,423 | 11,251 | 11,235 | 11,036 | 11,024 | 10,874 | 10,706 | 10,658 | 10,748 | 10,794 | 10,741 | 10,719 | 10,735 | 10,676 | 10,748 | 10,694 | 10,797 | 10,901 | 10,854 | 10,870 | 10,857 | 10,895 | 10,802 | 10,749 | 10,758 | 10,675 | 10,588 | 10,591 | 10,510 | 10,473 | 10,442 | 10,682 | 10,753 | 10,751 | 10,739 | 10,652 | 10,467 | 10,459 | 10,388 | 10,263 | 10,190 | 10,079 | 10,130 | 10,167 | 10,134 | 10,095 | 10,125 | 10,066 | 10,180 | 10,197 | 10,209 | 10,167 | 10,227 | 10,036 | 10,054 | 10,000 |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 11,974 | 12,253 | 12,087 | 11,911 | 11,647 | 11,542 | 11,353 | 11,625 | 11,512 | 11,652 | 11,680 | 11,253 | 10,768 | 10,932 | 11,200 | 11,267 | 11,256 | 11,274 | 11,392 | 11,323 | 11,063 | 11,342 | 11,001 | 11,038 | 10,641 | 10,759 | 11,244 | 11,544 | 11,261 | 11,490 | 11,427 | 11,870 | 12,197 | 12,366 | 12,643 | 12,652 | 12,636 | 12,647 | 12,756 | 12,764 | 12,637 | 12,546 | 12,498 | 12,394 | 12,540 | 12,704 | 12,784 | 12,740 | 12,576 | 12,621 | 12,644 | 12,717 | 12,498 | 12,394 | 12,280 | 12,039 | 12,278 | 12,097 | 11,884 | 11,866 | 11,869 | 11,830 | 11,882 | 11,619 | 11,585 | 11,423 | 11,251 | 11,235 | 11,036 | 11,024 | 10,874 | 10,706 | 10,658 | 10,748 | 10,794 | 10,741 | 10,719 | 10,735 | 10,676 | 10,748 | 10,694 | 10,797 | 10,901 | 10,854 | 10,870 | 10,857 | 10,895 | 10,802 | 10,749 | 10,758 | 10,675 | 10,588 | 10,591 | 10,510 | 10,473 | 10,442 | 10,682 | 10,753 | 10,751 | 10,739 | 10,652 | 10,467 | 10,459 | 10,388 | 10,263 | 10,190 | 10,079 | 10,130 | 10,167 | 10,134 | 10,095 | 10,125 | 10,066 | 10,180 | 10,197 | 10,209 | 10,167 | 10,227 | 10,036 | 10,054 | 10,000 |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 1,197,428 | 1,225,257 | 1,208,679 | 1,191,145 | 1,164,708 | 1,154,158 | 1,135,338 | 1,162,504 | 1,151,201 | 1,165,171 | 1,167,966 | 1,125,268 | 1,076,807 | 1,093,247 | 1,119,953 | 1,126,738 | 1,125,619 | 1,127,371 | 1,139,182 | 1,132,265 | 1,106,311 | 1,134,180 | 1,100,056 | 1,103,805 | 1,064,128 | 1,075,933 | 1,124,375 | 1,154,385 | 1,126,073 | 1,149,034 | 1,142,746 | 1,187,019 | 1,219,743 | 1,236,603 | 1,264,322 | 1,265,175 | 1,263,649 | 1,264,683 | 1,275,575 | 1,276,427 | 1,263,738 | 1,254,592 | 1,249,825 | 1,239,403 | 1,253,996 | 1,270,388 | 1,278,423 | 1,274,024 | 1,257,613 | 1,262,124 | 1,264,402 | 1,271,736 | 1,249,782 | 1,239,440 | 1,227,971 | 1,203,856 | 1,227,840 | 1,209,727 | 1,188,398 | 1,186,629 | 1,186,867 | 1,183,044 | 1,188,192 | 1,161,901 | 1,158,453 | 1,142,296 | 1,125,062 | 1,123,489 | 1,103,561 | 1,102,360 | 1,087,367 | 1,070,617 | 1,065,824 | 1,074,815 | 1,079,440 | 1,074,148 | 1,071,905 | 1,073,462 | 1,067,639 | 1,074,811 | 1,069,417 | 1,079,655 | 1,090,145 | 1,085,360 | 1,087,005 | 1,085,702 | 1,089,536 | 1,080,216 | 1,074,863 | 1,075,775 | 1,067,538 | 1,058,753 | 1,059,108 | 1,050,999 | 1,047,304 | 1,044,202 | 1,068,213 | 1,075,347 | 1,075,091 | 1,073,933 | 1,065,155 | 1,046,728 | 1,045,911 | 1,038,833 | 1,026,256 | 1,019,017 | 1,007,891 | 1,012,952 | 1,016,659 | 1,013,420 | 1,009,468 | 1,012,452 | 1,006,590 | 1,017,951 | 1,019,735 | 1,020,920 | 1,016,723 | 1,022,684 | 1,003,580 | 1,005,397 | 1,000,000 |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 12,556 | 12,639 | 12,503 | 12,428 | 12,297 | 12,217 | 12,090 | 12,119 | 12,047 | 12,094 | 12,040 | 11,898 | 11,761 | 11,719 | 11,753 | 11,748 | 11,689 | 11,727 | 11,830 | 11,798 | 11,554 | 11,622 | 11,541 | 11,568 | 11,509 | 11,394 | 11,846 | 11,997 | 11,773 | 11,985 | 11,950 | 11,985 | 12,068 | 11,930 | 12,020 | 11,996 | 11,966 | 11,888 | 11,901 | 11,899 | 11,723 | 11,730 | 11,631 | 11,523 | 11,447 | 11,462 | 11,392 | 11,274 | 11,202 | 11,232 | 11,259 | 11,111 | 11,015 | 10,925 | 10,846 | 10,707 | 10,899 | 10,836 | 10,779 | 10,694 | 10,686 | 10,654 | 10,691 | 10,626 | 10,628 | 10,556 | 10,491 | 10,440 | 10,353 | 10,341 | 10,258 | 10,240 | 10,236 | 10,281 | 10,314 | 10,258 | 10,279 | 10,265 | 10,224 | 10,232 | 10,171 | 10,180 | 10,217 | 10,200 | 10,221 | 10,204 | 10,222 | 10,189 | 10,155 | 10,207 | 10,214 | 10,214 | 10,197 | 10,186 | 10,134 | 10,104 | 10,166 | 10,163 | 10,087 | 10,125 | 10,136 | 10,022 | 10,040 | 10,038 | 9,922 | 9,896 | 9,824 | 9,853 | 9,874 | 9,874 | 9,887 | 9,912 | 9,947 | 9,951 | 9,957 | 9,883 | 9,917 | 9,946 | 9,838 | 9,981 | 10,000 |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 12,556 | 12,639 | 12,503 | 12,428 | 12,297 | 12,217 | 12,090 | 12,119 | 12,047 | 12,094 | 12,040 | 11,898 | 11,761 | 11,719 | 11,753 | 11,748 | 11,689 | 11,727 | 11,830 | 11,798 | 11,554 | 11,622 | 11,541 | 11,568 | 11,509 | 11,394 | 11,846 | 11,997 | 11,773 | 11,985 | 11,950 | 11,985 | 12,068 | 11,930 | 12,020 | 11,996 | 11,966 | 11,888 | 11,901 | 11,899 | 11,723 | 11,730 | 11,631 | 11,523 | 11,447 | 11,462 | 11,392 | 11,274 | 11,202 | 11,232 | 11,259 | 11,111 | 11,015 | 10,925 | 10,846 | 10,707 | 10,899 | 10,836 | 10,779 | 10,694 | 10,686 | 10,654 | 10,691 | 10,626 | 10,628 | 10,556 | 10,491 | 10,440 | 10,353 | 10,341 | 10,258 | 10,240 | 10,236 | 10,281 | 10,314 | 10,258 | 10,279 | 10,265 | 10,224 | 10,232 | 10,171 | 10,180 | 10,217 | 10,200 | 10,221 | 10,204 | 10,222 | 10,189 | 10,155 | 10,207 | 10,214 | 10,214 | 10,197 | 10,186 | 10,134 | 10,104 | 10,166 | 10,163 | 10,087 | 10,125 | 10,136 | 10,022 | 10,040 | 10,038 | 9,922 | 9,896 | 9,824 | 9,853 | 9,874 | 9,874 | 9,887 | 9,912 | 9,947 | 9,951 | 9,957 | 9,883 | 9,917 | 9,946 | 9,838 | 9,981 | 10,000 |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Account Value | $ 1,255,640 | $ 1,263,941 | $ 1,250,264 | $ 1,242,775 | $ 1,229,705 | $ 1,221,748 | $ 1,209,028 | $ 1,211,865 | $ 1,204,668 | $ 1,209,402 | $ 1,203,967 | $ 1,189,765 | $ 1,176,105 | $ 1,171,873 | $ 1,175,329 | $ 1,174,809 | $ 1,168,855 | $ 1,172,672 | $ 1,182,970 | $ 1,179,823 | $ 1,155,382 | $ 1,162,200 | $ 1,154,068 | $ 1,156,789 | $ 1,150,928 | $ 1,139,405 | $ 1,184,622 | $ 1,199,700 | $ 1,177,296 | $ 1,198,451 | $ 1,195,018 | $ 1,198,462 | $ 1,206,833 | $ 1,192,987 | $ 1,201,982 | $ 1,199,636 | $ 1,196,635 | $ 1,188,766 | $ 1,190,051 | $ 1,189,905 | $ 1,172,276 | $ 1,173,040 | $ 1,163,093 | $ 1,152,265 | $ 1,144,658 | $ 1,146,246 | $ 1,139,171 | $ 1,127,350 | $ 1,120,199 | $ 1,123,235 | $ 1,125,914 | $ 1,111,075 | $ 1,101,549 | $ 1,092,524 | $ 1,084,585 | $ 1,070,727 | $ 1,089,880 | $ 1,083,616 | $ 1,077,878 | $ 1,069,413 | $ 1,068,620 | $ 1,065,374 | $ 1,069,063 | $ 1,062,566 | $ 1,062,829 | $ 1,055,631 | $ 1,049,064 | $ 1,043,980 | $ 1,035,323 | $ 1,034,126 | $ 1,025,819 | $ 1,024,045 | $ 1,023,642 | $ 1,028,055 | $ 1,031,365 | $ 1,025,819 | $ 1,027,915 | $ 1,026,467 | $ 1,022,433 | $ 1,023,216 | $ 1,017,145 | $ 1,017,968 | $ 1,021,715 | $ 1,020,023 | $ 1,022,095 | $ 1,020,396 | $ 1,022,200 | $ 1,018,925 | $ 1,015,545 | $ 1,020,741 | $ 1,021,424 | $ 1,021,383 | $ 1,019,737 | $ 1,018,616 | $ 1,013,403 | $ 1,010,420 | $ 1,016,619 | $ 1,016,287 | $ 1,008,704 | $ 1,012,469 | $ 1,013,642 | $ 1,002,242 | $ 1,004,040 | $ 1,003,765 | $ 992,248 | $ 989,615 | $ 982,388 | $ 985,284 | $ 987,420 | $ 987,374 | $ 988,652 | $ 991,180 | $ 994,729 | $ 995,120 | $ 995,721 | $ 988,261 | $ 991,728 | $ 994,624 | $ 983,836 | $ 998,068 | $ 1,000,000 |
| Shareholder Report, Average Annual Return (Details) | 12 Months Ended | 60 Months Ended | 120 Months Ended |
| Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | |
| C000086684 | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Class A with Maximum Sales Charge | ||
| Average Annual Return, Percent | 3.79% | 3.58% | 2.54% |
| C000086685 | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Class C | ||
| Average Annual Return, Percent | 5.49% | 3.51% | 2.26% |
| C000086686 | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Class I | ||
| Without Sales Load [Member] | C000086684 | |||
| Average Annual Return [Line Items] | |||
| Average Annual Return, Percent | 7.32% | 4.27% | 2.89% |
| Without Sales Load [Member] | C000086685 | |||
| Average Annual Return [Line Items] | |||
| Average Annual Return, Percent | 6.49% | 3.51% | 2.26% |
| Without Sales Load [Member] | C000086686 | |||
| Average Annual Return [Line Items] | |||
| Average Annual Return, Percent | 7.58% | 4.54% | 3.14% |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||
| Average Annual Return, Percent | 11.20% | 0.18% | 1.82% |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||
| Average Annual Return, Percent | 11.20% | 0.18% | 1.82% |
| EATON VANCE Index: Bloomberg U.S. Universal Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Bloomberg U.S. Universal Index | ||
| Average Annual Return, Percent | 11.20% | 0.18% | 1.82% |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||
| Average Annual Return, Percent | 6.76% | 3.27% | 2.30% |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||
| Average Annual Return, Percent | 6.76% | 3.27% | 2.30% |
| EATON VANCE Index: ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | ICE BofA 1–5 Year U.S. Inflation-Linked Treasury Index | ||
| Average Annual Return, Percent | 6.76% | 3.27% | 2.30% |
| Shareholder Report, Holdings (Details) | Oct. 31, 2024 |
| C000086684 | FR_TSR_AT_FJ556 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (2.90%) |
| C000086684 | FR_TSR_AT_FJ555 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| C000086684 | FR_TSR_AT_FJ554 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| C000086684 | FR_TSR_AT_FJ553 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| C000086684 | FR_TSR_AT_FJ552 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.60% |
| C000086684 | FR_TSR_AT_FJ551 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 74.30% |
| C000086685 | FR_TSR_AT_FJ556 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (2.90%) |
| C000086685 | FR_TSR_AT_FJ555 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| C000086685 | FR_TSR_AT_FJ554 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| C000086685 | FR_TSR_AT_FJ553 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| C000086685 | FR_TSR_AT_FJ552 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.60% |
| C000086685 | FR_TSR_AT_FJ551 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 74.30% |
| C000086686 | FR_TSR_AT_FJ556 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (2.90%) |
| C000086686 | FR_TSR_AT_FJ555 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| C000086686 | FR_TSR_AT_FJ554 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| C000086686 | FR_TSR_AT_FJ553 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| C000086686 | FR_TSR_AT_FJ552 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.60% |
| C000086686 | FR_TSR_AT_FJ551 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 74.30% |
