| Shareholder Report | 12 Months Ended | 119 Months Ended |
| Jun. 30, 2024 USD ($) Holding | Jun. 30, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | | |
| Document Type | N-CSR | |
| Amendment Flag | false | |
| Registrant Name | Forum Funds II | |
| Entity Central Index Key | 0001576367 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Jun. 30, 2024 | |
| C000142990 | | |
| Shareholder Report [Line Items] | | |
| Fund Name | Acuitas US Microcap Fund | |
| Class Name | Institutional | |
| Trading Symbol | AFMCX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Acuitas US Microcap Fund for the period of July 1, 2023, to June 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | This annual shareholder report contains important information about the Acuitas US Microcap Fund for the period of July 1, 2023, to June 30, 2024. You can find additional information about the Fund at https://acuitasfunds.com/invest-with-us | |
| Additional Information Phone Number | (844) 805-5628 | |
| Additional Information Website | https://acuitasfunds.com/invest-with-us</span>/ " id="sjs-B19" xml:space="preserve"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: justify;">https://acuitasfunds.com/invest-with-us</span>/ | |
| Expenses [Text Block] | What were the Fund's costs for the last year? (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 Institutional Shares $155 1.50% | |
| Expenses Paid, Amount | $ 155 | |
| Expense Ratio, Percent | 1.50% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform in the last year? The Fund returned +6.63% over the last year, outperforming the Russell Microcap Index’s return of +5.96% by 67 basis points. Strong stock selection across our subadvisers drove the Fund’s excess returns, with stock picks in financials, technology, consumer discretionary, and basic materials adding the most value relative to the benchmark. We are proud that the Fund has consistently outperformed the benchmark over various time horizons, including the 1-, 3-, and 5- year periods. Additionally, since the Fund’s inception on 7/18/14, the Fund has returned an annualized 7.80% net of fees, outperforming the benchmark’s 6.02% return by an annualized 178 basis points. | |
| Performance Past Does Not Indicate Future [Text] | The Fund’s past performance is not a good predictor of how the Fund will perform in the future. | |
| Line Graph [Table Text Block] | Date Institutional Shares Russell Microcap ® Russell 3000 Index 07/18/14 $10,000 $10,000 $10,000 09/30/14 $9,520 $9,581 $9,963 12/31/14 $10,470 $10,653 $10,485 03/31/15 $11,000 $10,988 $10,674 06/30/15 $11,270 $11,295 $10,688 09/30/15 $10,320 $9,739 $9,914 12/31/15 $10,727 $10,103 $10,535 03/31/16 $10,311 $9,555 $10,637 06/30/16 $10,789 $9,933 $10,917 09/30/16 $11,693 $11,051 $11,397 12/31/16 $13,039 $12,161 $11,877 03/31/17 $12,808 $12,207 $12,559 06/30/17 $13,186 $12,676 $12,938 09/30/17 $14,161 $13,519 $13,529 12/31/17 $14,376 $13,763 $14,386 03/31/18 $14,224 $13,856 $14,294 06/30/18 $15,397 $15,237 $14,849 09/30/18 $15,864 $15,364 $15,907 12/31/18 $12,523 $11,962 $13,632 03/31/19 $14,170 $13,529 $15,547 06/30/19 $13,907 $13,654 $16,183 09/30/19 $13,589 $12,910 $16,371 12/31/19 $15,264 $14,645 $17,861 03/31/20 $9,613 $9,961 $14,128 06/30/20 $12,134 $13,003 $17,240 09/30/20 $12,937 $13,483 $18,827 12/31/20 $17,411 $17,715 $21,592 03/31/21 $21,746 $21,947 $22,962 06/30/21 $23,201 $22,856 $24,854 09/30/21 $22,009 $21,718 $24,829 12/31/21 $22,511 $21,141 $27,132 03/31/22 $20,614 $19,535 $25,700 06/30/22 $17,361 $15,831 $21,408 09/30/22 $17,166 $15,755 $20,452 12/31/22 $18,199 $16,499 $21,921 03/31/23 $18,871 $16,033 $23,495 06/30/23 $19,799 $16,882 $25,465 09/30/23 $18,999 $15,542 $24,637 12/31/23 $21,368 $18,039 $27,611 03/31/24 $22,649 $18,884 $30,377 06/30/24 $21,112 $17,887 $31,354 | |
| Average Annual Return [Table Text Block] | One Year Five Year Since Inception
07/18/14 Institutional Shares 6.63% 8.71% 7.80% Russell Microcap ® 5.96% 5.55% 6.02% Russell 3000 Index 23.13% 14.14% 12.17% | |
| Performance Inception Date | | Jul. 18, 2014 |
| 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. | |
| Performance Table Market Index Changed [Text Block] | Effective June 12, 2024, the Fund changed its primary benchmark index from the Russell Microcap ® ® ® ® | |
| Prior Market Index Comparison [Text Block] | The Fund retained the Russell Microcap ® | |
| Updated Performance Information Location [Text Block] | | |
| AssetsNet | $ 82,567,532 | $ 82,567,532 |
| Holdings Count | Holding | 234 | 234 |
| Advisory Fees Paid, Amount | $ 565,156 | |
| InvestmentCompanyPortfolioTurnover | 64% | |
| Additional Fund Statistics [Text Block] | Fund Statistics Total Net Assets $82,567,532 # of Portfolio Holdings 234 Portfolio Turnover Rate 64% Investment Advisory Fees (Net of fees waived)
$565,156 | |
| Holdings [Text Block] | Sector Weightings (% total investments)* Value Value Industrials 23.2% Health Care 20.2% Technology 15.7% Financials 13.2% Consumer Discretionary 11.4% Energy 6.5% Utilities 2.6% Basic Materials 2.5% Real Estate 2.4% Consumer Staples 1.9% Telecommunications 0.4% * excluding cash equivalents | |
| Largest Holdings [Text Block] | Top Ten Holdings (% of investments)* Columbus McKinnon Corp. 1.72% Photronics, Inc. 1.54% Select Water Solutions, Inc., Class A 1.53% BioLife Solutions, Inc. 1.52% Magnite, Inc. 1.46% Interface, Inc. 1.43% Ducommun, Inc. 1.26% Customers Bancorp, Inc. 1.21% Civitas Resources, Inc. 1.17% Barrett Business Services, Inc. 1.13% * excluding cash equivalents | |
| Updated Prospectus Web Address | https://acuitasfunds.com/invest-with-us</span>/ " id="sjs-B39" xml:space="preserve"><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;">https://acuitasfunds.com/invest-with-us</span>/ | |
