v3.26.1
Shareholder Report
 6 Months Ended
May 31, 2026
USD ($)
shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Fidelity Commonwealth Trust
Entity Central Index Key 0000205323
Entity Investment Company Type N-1A
Document Period End Date May 31, 2026
Fidelity Nasdaq Composite Index ETF  
Shareholder Report [Line Items]  
Fund Name Fidelity® Nasdaq Composite Index® ETF
Class Name Fidelity® Nasdaq Composite Index® ETF
Trading Symbol ONEQ
Security Exchange Name NASDAQ
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains information about Fidelity® Nasdaq Composite Index® ETF for the period December 1, 2025 to May 31, 2026.
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-FIDELITY or by sending an e-mail to fidfunddocuments@fidelity.com.
Additional Information Phone Number 1-800-FIDELITY
Additional Information Email fidfunddocuments@fidelity.com
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® Nasdaq Composite Index® ETF 
$ 11 
0.21%
  
Expenses Paid, Amount $ 11
Expense Ratio, Percent 0.21%
Net Assets $ 10,922,502,914
Holdings Count | shares 1,025
Investment Company Portfolio Turnover 6.00%
Additional Fund Statistics [Text Block] Key Fund Statistics
(as of May 31, 2026)
 
KEY FACTS 
  
  
Fund Size
$10,922,502,914
  
Number of Holdings
1,025
  
Portfolio Turnover
6%
  
Holdings [Text Block]       MARKET SECTORS (% of Fund's net assets)     Information Technology 54.0   Communication Services 14.8   Consumer Discretionary 12.8   Health Care 4.6   Consumer Staples 4.4   Industrials 3.3   Financials 2.9   Materials 0.9   Utilities 0.8   Real Estate 0.5   Energy 0.5     Common Stocks 99.5 Short-Term Investments and Net Other Assets (Liabilities) 0.5 ASSET ALLOCATION (% of Fund's net assets)     Common Stocks - 99.5                       Short-Term Investments and Net Other Assets (Liabilities) - 0.5   United States 97.1 Netherlands 0.8 Canada 0.6 Israel 0.4 China 0.4 Brazil 0.3 United Kingdom 0.1 Switzerland 0.1 Kazakhstan 0.1 Others 0.1 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets)     United States - 97.1                       Netherlands - 0.8                          Canada - 0.6                               Israel - 0.4                               China - 0.4                                Brazil - 0.3                               United Kingdom - 0.1                       Switzerland - 0.1                          Kazakhstan - 0.1                           Others - 0.1                                  
Largest Holdings [Text Block] TOP HOLDINGS(% of Fund's net assets)     NVIDIA Corp 11.3   Apple Inc 10.0   Microsoft Corp 7.4   Amazon.com Inc 6.4   Alphabet Inc Class A 4.9   Broadcom Inc 4.7   Alphabet Inc Class C 4.5   Tesla Inc 3.6   Meta Platforms Inc Class A 3.1   Micron Technology Inc 2.5     58.4