| Document and Entity Information | Aug. 15, 2024 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 15, 2024 |
| Current Fiscal Year End Date | --12-31 |
| Entity File Number | 001-42252 |
| Entity Registrant Name | HCM II Acquisition Corp. |
| Entity Central Index Key | 0002019804 |
| Entity Incorporation, State or Country Code | E9 |
| Entity Tax Identification Number | 98-1785406 |
| Entity Address, Address Line One | 100 First Stamford Place |
| Entity Address, City or Town | Stamford |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06902 |
| City Area Code | 203 |
| Local Phone Number | 930-2200 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Units, each consisting of one Class A ordinary share and one-half of one Redeemable Warrant [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Units, each consisting of one Class A ordinary share and one-half of one Redeemable Warrant |
| Trading Symbol | HONDU |
| Security Exchange Name | NASDAQ |
| Class A Ordinary Shares, par value $0.0001 per share [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Class A Ordinary Shares, par value $0.0001 per share |
| Trading Symbol | HOND |
| Security Exchange Name | NASDAQ |
| Redeemable Warrants, each whole warrant exercisable for one Class A ordinary share at a price of $11.50 per share [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Redeemable Warrants, each whole warrant exercisable for one Class A ordinary share at a price of $11.50 per share |
| Trading Symbol | HONDW |
| Security Exchange Name | NASDAQ |
