| Cover | May 12, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | May 12, 2021 |
| 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 |
| Entity Address, Address Line Two | 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 | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001774155 |
| Amendment Flag | false |
| Common Class 1 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Class 1 Common Stock, $0.0001 par value per share |
| Trading Symbol | BTRS |
| Security Exchange Name | NASDAQ |
| Warrant | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each whole warrant exercisable for one share of Class 1 Common Stock at an exercise price of $11.50 per share |
| Trading Symbol | BTRSW |
| Security Exchange Name | NASDAQ |
