| Document and Entity Information | Nov. 18, 2021 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 18, 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, 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 | true |
| 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 |
| The Nasdaq Global Select Market [Member] | Common Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Class 1 Common Stock, par value $0.0001 per share |
| Trading Symbol | BTRS |
| Security Exchange Name | NASDAQ |
| The Nasdaq Capital Market [Member] | Warrants, each whole warrant exercisable for one share of Class 1 Common Stock at an exercise price of $11.50 per share [Member] | |
| Entity Listings [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 |
