| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Stock Portfolio |
| Entity Central Index Key | 0001473646 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 6 Months Ended |
| Jun. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Stock Portfolio |
| Entity Central Index Key | 0001473646 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| C000081816 | |
| Shareholder Report [Line Items] | |
| Fund Name | Stock Portfolio |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Stock Portfolio (the "Fund") for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-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-B17"><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 six months? (based on a hypothetical $10,000 investment) Fund Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Stock Portfolio $35 0.63% |
| Expenses Paid, Amount | $ 35 |
| Expense Ratio, Percent | 0.63% |
| AssetsNet | $ 703,812,222 |
| Holdings Count | Holding | 53 |
| InvestmentCompanyPortfolioTurnover | 19% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $703,812,222 # of Portfolio Holdings 53 Portfolio Turnover Rate 19% |
| Holdings [Text Block] | Sector Allocation (% of total investments) Value Value Utilities 1.5% Short-Term Investments 1.6% Real Estate 1.9% Materials 2.0% Energy 2.0% Consumer Staples 3.8% Consumer Discretionary 8.8% Industrials 11.1% Communication Services 11.2% Health Care 11.8% Financials 12.2% Information Technology 32.1% |
| Largest Holdings [Text Block] | Top Ten Holdings (% of total investments) Footnote Reference Microsoft Corp. 8.4% Apple, Inc. 7.2% NVIDIA Corp. 7.2% Alphabet, Inc., Class C 4.8% Amazon.com, Inc. 4.7% Meta Platforms, Inc., Class A 2.9% Broadcom, Inc. 2.6% Eli Lilly & Co. 2.5% AbbVie, Inc. 2.4% Walmart, Inc. 2.4% Total 45.1% Footnote Description Footnote a Excluding cash equivalents |
| Material Fund Change [Text Block] |
| Shareholder Report, Holdings (Details) - C000081816 | Jun. 30, 2024 |
| FR_594918104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.40% |
| FR_037833100 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.20% |
| FR_67066G104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.20% |
| FR_02079K107 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| FR_023135106 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| FR_30303M102 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| FR_11135F101 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| FR_532457108 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| FR_00287Y109 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.40% |
| FR_931142103 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.40% |
| SectorUtilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| SectorReal Estate | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| SectorMaterials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| SectorEnergy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| SectorConsumer Staples | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.80% |
| SectorConsumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.80% |
| SectorIndustrials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.10% |
| SectorCommunication Services | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.20% |
| SectorHealth Care | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.80% |
| SectorFinancials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.20% |
| SectorInformation Technology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.10% |
