| Cover | Jun. 24, 2021 | May 12, 2021 |
| Document Information [Line Items] | ||
| Document Type | 8-K | |
| Document Period End Date | Jun. 24, 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 |
