| Cover | Jul. 22, 2021 |
| Affiliate, Collateralized Security [Line Items] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Document Period End Date | Jul. 22, 2021 |
| Entity Registrant Name | Sema4 Holdings Corp. |
| Entity Central Index Key | 0001818331 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39482 |
| Entity Tax Identification Number | 85-1966622 |
| Entity Address, Address Line One | 333 Ludlow Street, North Tower, 8th Floor |
| Entity Address, City or Town | Stamford, |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06902 |
| City Area Code | 800 |
| Local Phone Number | 298-6470 |
| Entity Information, Former Legal or Registered Name | CM Life Sciences, Inc. |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Amendment Description | This Amendment No. 1 on Form 8-K/A to the Original 8-K (this “Amendment” and the Original 8-K, as amended by this Amendment, this “Report”) is being filed to (a) provide updated financial statements including (i) the unaudited financial statements of Sema4 for the three and six months ended June 30, 2021, and (ii) the pro forma financial statements for the combined entities as of and for the three and six months ended June 30, 2021 and for the year ended December 31, 2020, and (b) amend the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” which was part of the Form 10 information disclosed under and incorporated by reference to Item 2.01 to the Original 8-K to reflect such unaudited financial statements. |
| Former Address | |
| Affiliate, Collateralized Security [Line Items] | |
| Entity Address, Address Line One | 667 Madison Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Class A common stock, par value $0.0001 per share | |
| Affiliate, Collateralized Security [Line Items] | |
| Title of 12(b) Security | Class A common stock, par value $0.0001 per share |
| Trading Symbol | SMFR |
| Security Exchange Name | NASDAQ |
| Warrants to purchase one share of Class A common stock, each at an exercise price of $11.50 per share | |
| Affiliate, Collateralized Security [Line Items] | |
| Title of 12(b) Security | Warrants to purchase one share of Class A common stock, each at an exercise price of $11.50 per share |
| Trading Symbol | SMFRW |
| Security Exchange Name | NASDAQ |
