v3.25.2
Shareholder Report
 6 Months Ended
Jun. 30, 2025
USD ($)
shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Fidelity Hastings Street Trust
Entity Central Index Key 0000035348
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2025
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 semi-annual shareholder report contains information about Fidelity® Series Emerging Markets Debt Local Currency Fund for the period January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual semi-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 six months?
(based on hypothetical $10,000 investment)
 
 
 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
 
Fidelity® Series Emerging Markets Debt Local Currency Fund 
$ 0 A
0.00%B
  
A Amount represents less than $.50
B Amount represents less than 0.005%
 
Expenses Paid, Amount $ 0
Expense Ratio, Percent 0.00%
Net Assets $ 453,868,409
Holdings Count | shares 243
Investment Company Portfolio Turnover 68.00%
Additional Fund Statistics [Text Block] Key Fund Statistics
(as of June 30, 2025)
 
KEY FACTS 
  
  
Fund Size
$453,868,409
  
Number of Holdings
243
  
Portfolio Turnover
68%
  
Holdings [Text Block]   U.S. Government and U.S. Government Agency Obligations 0.4 AAA 2.0 AA 5.0 A 3.4 BBB 16.9 BB 10.5 Not Rated 49.8 Short-Term Investments and Net Other Assets (Liabilities) 12.0 QUALITY DIVERSIFICATION (% of Fund's net assets)     U.S. Government and U.S. Government Agency Obligations - 0.4   AAA - 2.0                                  AA - 5.0                                   A - 3.4                                    BBB - 16.9                                 BB - 10.5                                  Not Rated - 49.8                           Short-Term Investments and Net Other Assets (Liabilities) - 12.0   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 85.0 Corporate Bonds 2.6 U.S. Treasury Obligations 0.4 Short-Term Investments and Net Other Assets (Liabilities) 12.0 ASSET ALLOCATION (% of Fund's net assets)     Foreign Government and Government Agency Obligations - 85.0   Corporate Bonds - 2.6                      U.S. Treasury Obligations - 0.4            Short-Term Investments and Net Other Assets (Liabilities) - 12.0   United States 12.4 Indonesia 9.8 Malaysia 9.4 Mexico 8.6 Brazil 7.6 South Africa 6.8 India 6.6 Thailand 4.9 China 4.8 Others 29.1 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets)     United States - 12.4                       Indonesia - 9.8                            Malaysia - 9.4                             Mexico - 8.6                               Brazil - 7.6                               South Africa - 6.8                         India - 6.6                                Thailand - 4.9                             China - 4.8                                Others - 29.1                                 
Largest Holdings [Text Block] TOP HOLDINGS (% of Fund's net assets)     Indonesia Government 9.8   Malaysia Government 9.4   United Mexican States 8.6   South African Republic 6.8   Republic of India 6.6   Kingdom of Thailand 4.9   Peoples Republic of China 4.8   Republic of Poland 4.8   Czech Republic 4.4   Brazilian Federative Republic 4.0     64.1  
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 semi-annual shareholder report contains information about Fidelity® Series Emerging Markets Debt Fund for the period January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual semi-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 six months?
(based on hypothetical $10,000 investment)
 
 
 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
 
Fidelity® Series Emerging Markets Debt Fund 
$ 0 A
0.00%B
  
A Amount represents less than $.50
B Amount represents less than 0.005%
 
Expenses Paid, Amount $ 0
Expense Ratio, Percent 0.00%
Net Assets $ 1,458,939,256
Holdings Count | shares 486
Investment Company Portfolio Turnover 25.00%
Additional Fund Statistics [Text Block] Key Fund Statistics
(as of June 30, 2025)
 
KEY FACTS 
  
  
Fund Size
$1,458,939,256
  
Number of Holdings
486
  
Portfolio Turnover
25%
  
Holdings [Text Block]   U.S. Government and U.S. Government Agency Obligations 3.1 AA 8.4 A 3.5 BBB 19.5 BB 23.9 B 18.6 CCC,CC,C 12.7 D 0.2 Not Rated 3.6 Equities 0.1 Short-Term Investments and Net Other Assets (Liabilities) 6.4 QUALITY DIVERSIFICATION (% of Fund's net assets)     U.S. Government and U.S. Government Agency Obligations - 3.1   AA - 8.4                                   A - 3.5                                    BBB - 19.5                                 BB - 23.9                                  B - 18.6                                   CCC,CC,C - 12.7                            D - 0.2                                    Not Rated - 3.6                            Equities - 0.1                             Short-Term Investments and Net Other Assets (Liabilities) - 6.4   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 57.4 Corporate Bonds 31.3 U.S. Treasury Obligations 3.1 Preferred Securities 1.7 Preferred Stocks 0.1 Short-Term Investments and Net Other Assets (Liabilities) 6.4 ASSET ALLOCATION (% of Fund's net assets)     Foreign Government and Government Agency Obligations - 57.4   Corporate Bonds - 31.3                     U.S. Treasury Obligations - 3.1            Preferred Securities - 1.7                 Preferred Stocks - 0.1                     Short-Term Investments and Net Other Assets (Liabilities) - 6.4   United States 9.5 Mexico 7.6 Colombia 4.4 Brazil 4.3 Saudi Arabia 4.2 United Arab Emirates 3.9 Chile 3.9 Turkey 3.6 Dominican Republic 3.2 Others 55.4 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets)     United States - 9.5                        Mexico - 7.6                               Colombia - 4.4                             Brazil - 4.3                               Saudi Arabia - 4.2                         United Arab Emirates - 3.9                 Chile - 3.9                                Turkey - 3.6                               Dominican Republic - 3.2                   Others - 55.4                                 
Largest Holdings [Text Block] TOP HOLDINGS (% of Fund's net assets)     Petroleos Mexicanos 3.2   Turkish Republic 3.1   Dominican Republic 3.1   Argentine Republic 2.9   Arab Republic of Egypt 2.7   Colombian Republic 2.6   Republic of Nigeria 2.5   Oman Sultanate 2.1   United Mexican States 2.0   Indonesia Government 1.8     26.0