| Form N-CSR Cover | 12 Months Ended |
| Dec. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Hastings Street Trust |
| Entity Central Index Key | 0000035348 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Shareholder Report | 12 Months Ended |
| Dec. 31, 2024 USD ($) shares | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Hastings Street Trust |
| Entity Central Index Key | 0000035348 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Fidelity Series Emerging Markets Debt Local Currency Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Series Emerging Markets Debt Local Currency Fund |
| Class Name | Fidelity® Series Emerging Markets Debt Local Currency Fund |
| Trading Symbol | FSEDX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Series Emerging Markets Debt Local Currency Fund for the period January 1, 2024 to December 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Series Emerging Markets Debt Local Currency Fund $ A 0.00 % B A Amount represents less than $.50 B Amount represents less than 0.005% |
| Expenses Paid, Amount | $ 0 |
| Expense Ratio, Percent | 0% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B24"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE October 30, 2020 through December 31, 2024. Initial investment of $10,000. Fidelity® Series Emerging Markets Debt Local Currency Fund $10,000 $10,874 $9,943 $9,162 $10,402 J.P. Morgan GBI-EM Global Diversified Index $10,000 $10,916 $9,961 $8,797 $9,914 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year Life of Fund A Fidelity® Series Emerging Markets Debt Local Currency Fund -2.54% 0.33% J.P. Morgan GBI-EM Global Diversified Index -2.38% -0.78% A From October 30, 2020 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Oct. 30, 2020 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 406,375,132 |
| Holdings Count | shares | 234 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 46% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 234 Total Advisory Fee $ Portfolio Turnover 46 % |
| Holdings [Text Block] | U.S. Government and U.S. Government Agency Obligations 0.5 AAA 2.8 AA 4.7 A 4.2 BBB 18.9 BB 11.9 Not Rated 45.5 Short-Term Investments and Net Other Assets (Liabilities) 11.5 QUALITY DIVERSIFICATION (% of Fund's net assets) U.S. Government and U.S. Government Agency Obligations - 0.5 AAA - 2.8 AA - 4.7 A - 4.2 BBB - 18.9 BB - 11.9 Not Rated - 45.5 Short-Term Investments and Net Other Assets (Liabilities) - 11.5 We have used ratings from Moody's Investors Service, Inc. Where Moody's® ratings are not available, we have used S&P® ratings. All ratings are as of the date indicated and do not reflect subsequent changes. Foreign Government and Government Agency Obligations 84.8 Corporate Bonds 3.2 U.S. Treasury Obligations 0.5 Short-Term Investments and Net Other Assets (Liabilities) 11.5 ASSET ALLOCATION (% of Fund's net assets) Foreign Government and Government Agency Obligations - 84.8 Corporate Bonds - 3.2 U.S. Treasury Obligations - 0.5 Short-Term Investments and Net Other Assets (Liabilities) - 11.5 United States 12.0 Mexico 10.1 Malaysia 9.9 Indonesia 8.8 South Africa 8.3 Brazil 7.4 China 4.8 Poland 4.6 Romania 4.4 Others 29.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 12.0 Mexico - 10.1 Malaysia - 9.9 Indonesia - 8.8 South Africa - 8.3 Brazil - 7.4 China - 4.8 Poland - 4.6 Romania - 4.4 Others - 29.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) United Mexican States 10.1 Malaysia Government 9.9 Indonesia Government 8.8 South African Republic 8.3 Peoples Republic of China 4.8 Republic of Poland 4.6 Romanian Republic 4.4 Kingdom of Thailand 4.3 Czech Republic 4.3 Colombian Republic 4.2 63.7 |
| Fidelity Series Emerging Markets Debt Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Series Emerging Markets Debt Fund |
| Class Name | Fidelity® Series Emerging Markets Debt Fund |
| Trading Symbol | FEDCX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Series Emerging Markets Debt Fund for the period January 1, 2024 to December 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Series Emerging Markets Debt Fund $ A 0.00 % B A Amount represents less than $.50 B Amount represents less than 0.005% |
| Expenses Paid, Amount | $ 0 |
| Expense Ratio, Percent | 0% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B50"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years? CUMULATIVE PERFORMANCE December 31, 2014 through December 31, 2024. Initial investment of $10,000. Fidelity® Series Emerging Markets Debt Fund $10,000 $10,151 $11,745 $12,996 $12,390 $13,687 $14,337 $14,251 $12,191 $13,711 $14,792 J.P. Morgan Emerging Markets Bond Index Global Diversified Linked Index $10,000 $10,123 $11,155 $12,194 $11,632 $13,309 $14,092 $13,879 $11,667 $12,961 $13,809 J.P. Morgan Emerging Markets Bond Index Global Diversified $10,000 $10,118 $11,146 $12,289 $11,765 $13,534 $14,246 $13,990 $11,502 $12,778 $13,613 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year 10 Year Fidelity® Series Emerging Markets Debt Fund 7.89% 1.57% 3.99% J.P. Morgan Emerging Markets Bond Index Global Diversified Linked Index 6.54% 0.74% 3.28% J.P. Morgan Emerging Markets Bond Index Global Diversified 6.54% 0.12% 3.13% Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 1,381,513,336 |
| Holdings Count | shares | 473 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 18% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 473 Total Advisory Fee $ Portfolio Turnover 18 % |
| Holdings [Text Block] | U.S. Government and U.S. Government Agency Obligations 3.5 AA 9.4 A 3.0 BBB 19.4 BB 24.4 B 17.0 CCC,CC,C 16.0 D 0.1 Not Rated 2.6 Short-Term Investments and Net Other Assets (Liabilities) 4.6 QUALITY DIVERSIFICATION (% of Fund's net assets) U.S. Government and U.S. Government Agency Obligations - 3.5 AA - 9.4 A - 3.0 BBB - 19.4 BB - 24.4 B - 17.0 CCC,CC,C - 16.0 D - 0.1 Not Rated - 2.6 Short-Term Investments and Net Other Assets (Liabilities) - 4.6 We have used ratings from Moody's Investors Service, Inc. Where Moody's® ratings are not available, we have used S&P® ratings. All ratings are as of the date indicated and do not reflect subsequent changes. Foreign Government and Government Agency Obligations 58.0 Corporate Bonds 32.6 U.S. Treasury Obligations 3.5 Preferred Securities 1.3 Short-Term Investments and Net Other Assets (Liabilities) 4.6 ASSET ALLOCATION (% of Fund's net assets) Foreign Government and Government Agency Obligations - 58.0 Corporate Bonds - 32.6 U.S. Treasury Obligations - 3.5 Preferred Securities - 1.3 Short-Term Investments and Net Other Assets (Liabilities) - 4.6 United States 8.1 Mexico 7.2 Brazil 4.7 Colombia 4.3 Saudi Arabia 4.2 United Arab Emirates 3.8 Chile 3.6 Turkey 3.6 Dominican Republic 3.4 Others 57.1 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 8.1 Mexico - 7.2 Brazil - 4.7 Colombia - 4.3 Saudi Arabia - 4.2 United Arab Emirates - 3.8 Chile - 3.6 Turkey - 3.6 Dominican Republic - 3.4 Others - 57.1 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Petroleos Mexicanos 3.7 Dominican Republic International Bond 3.3 Turkish Republic 3.2 Arab Republic of Egypt 3.0 Argentine Republic 2.9 Colombian Republic 2.8 Republic of Nigeria 2.7 Oman Sultanate 2.3 Panamanian Republic 2.0 Indonesia Government 1.9 27.8 |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | 132 Months Ended | ||||||||||
| Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
| C000221495_0_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | (2.38%) | |||||||||||||
| C000221495_0_BBIndexMember_LOCMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | (0.78%) | |||||||||||||
| C000098197_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 6.54% | |||||||||||||
| C000098197_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 0.12% | |||||||||||||
| C000098197_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 3.13% | |||||||||||||
| C000221495_LG_ClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Series Emerging Markets Debt Local Currency Fund</span>" id="sjs-C20"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Series Emerging Markets Debt Local Currency Fund</span> | |||||||||||||
| C000221495_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,000 | |||||||||||||
| C000221495_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,874 | |||||||||||||
| C000221495_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 9,943 | |||||||||||||
| C000221495_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 9,162 | |||||||||||||
| C000221495_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,402 | $ 10,402 | $ 10,402 | $ 10,402 | ||||||||||
| C000221495_LG_1_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | J.P. Morgan GBI-EM Global Diversified Index</span>" id="sjs-C38"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">J.P. Morgan GBI-EM Global Diversified Index</span> | |||||||||||||
| C000221495_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000221495_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,916 | |||||||||||||
| C000221495_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,961 | |||||||||||||
| C000221495_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 8,797 | |||||||||||||
| C000221495_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 9,914 | $ 9,914 | 9,914 | $ 9,914 | ||||||||||
| C000221495_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | (2.54%) | |||||||||||||
| C000221495_NoLoadClassMember_2024-01-01_2024-12-31Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 0.33% | |||||||||||||
| C000098197_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Series Emerging Markets Debt Fund</span>" id="sjs-E62"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Series Emerging Markets Debt Fund</span> | |||||||||||||
| C000098197_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,000 | |||||||||||||
| C000098197_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,151 | |||||||||||||
| C000098197_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,745 | |||||||||||||
| C000098197_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 12,996 | |||||||||||||
| C000098197_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 12,390 | |||||||||||||
| C000098197_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,687 | |||||||||||||
| C000098197_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 14,337 | |||||||||||||
| C000098197_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 14,251 | |||||||||||||
| C000098197_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,191 | |||||||||||||
| C000098197_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,711 | |||||||||||||
| C000098197_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 14,792 | 14,792 | 14,792 | $ 14,792 | ||||||||||
| C000098197_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | J.P. Morgan Emerging Markets Bond Index Global Diversified Linked Index</span>" id="sjs-E98"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">J.P. Morgan Emerging Markets Bond Index Global Diversified Linked Index</span> | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,123 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,155 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,194 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,632 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,309 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 14,092 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,879 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,667 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,961 | |||||||||||||
| C000098197_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,809 | 13,809 | 13,809 | $ 13,809 | ||||||||||
| C000098197_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | J.P. Morgan Emerging Markets Bond Index Global Diversified</span>" id="sjs-E134"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">J.P. Morgan Emerging Markets Bond Index Global Diversified</span> | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,000 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,118 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,146 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 12,289 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,765 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,534 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 14,246 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,990 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,502 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 12,778 | |||||||||||||
| C000098197_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,613 | $ 13,613 | $ 13,613 | $ 13,613 | ||||||||||
| C000098197_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 7.89% | |||||||||||||
| C000098197_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 1.57% | |||||||||||||
| C000098197_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 3.99% | |||||||||||||
| C000098197_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 6.54% | |||||||||||||
| C000098197_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 0.74% | |||||||||||||
| C000098197_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 3.28% |
| Shareholder Report, Holdings (Details) | Dec. 31, 2024 |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.10% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.40% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDUSGovernmentandUSGovernmentAgencyObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.50% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDAAAMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDAAMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDAMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDBBBMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.90% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDBBMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.90% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDNotRatedMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 45.50% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | QDShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Mexico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.10% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Malaysia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Indonesia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | South Africa | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.40% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Poland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | Romania | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.40% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 29.70% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | AAForeignGovernmentandGovernmentAgencyObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 84.80% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | AACorporateBondsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | AAUSTreasuryObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.50% |
| Fidelity Series Emerging Markets Debt Local Currency Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| Fidelity Series Emerging Markets Debt Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| Fidelity Series Emerging Markets Debt Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| Fidelity Series Emerging Markets Debt Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity Series Emerging Markets Debt Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Series Emerging Markets Debt Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity Series Emerging Markets Debt Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity Series Emerging Markets Debt Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity Series Emerging Markets Debt Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Fidelity Series Emerging Markets Debt Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity Series Emerging Markets Debt Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity Series Emerging Markets Debt Fund | QDUSGovernmentandUSGovernmentAgencyObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity Series Emerging Markets Debt Fund | QDAAMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.40% |
| Fidelity Series Emerging Markets Debt Fund | QDAMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Series Emerging Markets Debt Fund | QDBBBMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
| Fidelity Series Emerging Markets Debt Fund | QDBBMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 24.40% |
| Fidelity Series Emerging Markets Debt Fund | QDNotRatedMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity Series Emerging Markets Debt Fund | QDShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Series Emerging Markets Debt Fund | QDBMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17% |
| Fidelity Series Emerging Markets Debt Fund | QDCCCCCCMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16% |
| Fidelity Series Emerging Markets Debt Fund | QDDMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.10% |
| Fidelity Series Emerging Markets Debt Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.10% |
| Fidelity Series Emerging Markets Debt Fund | Mexico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.20% |
| Fidelity Series Emerging Markets Debt Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity Series Emerging Markets Debt Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 57.10% |
| Fidelity Series Emerging Markets Debt Fund | Colombia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity Series Emerging Markets Debt Fund | Saudi Arabia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| Fidelity Series Emerging Markets Debt Fund | United Arab Emirates | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.80% |
| Fidelity Series Emerging Markets Debt Fund | Chile | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Fidelity Series Emerging Markets Debt Fund | Turkey | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Fidelity Series Emerging Markets Debt Fund | Dominican Republic | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Series Emerging Markets Debt Fund | AAForeignGovernmentandGovernmentAgencyObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 58% |
| Fidelity Series Emerging Markets Debt Fund | AACorporateBondsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.60% |
| Fidelity Series Emerging Markets Debt Fund | AAUSTreasuryObligationsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity Series Emerging Markets Debt Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Series Emerging Markets Debt Fund | AAPreferredSecuritiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
