| Document and Entity Information | Apr. 22, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 22, 2022 |
| Entity Registrant Name | BTRS HOLDINGS INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38947 |
| Entity Tax Identification Number | 83-3780685 |
| Entity Address, Address Line One | 1009 Lenox Drive, Suite 101 |
| Entity Address, City or Town | Lawrenceville |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 08648 |
| City Area Code | 609 |
| Local Phone Number | 235-1010 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001774155 |
| Title of 12(b) Security | Class 1 Common Stock, $0.0001 par value per share |
| Trading Symbol | BTRS |
| Security Exchange Name | NASDAQ |
