| Cover | Oct. 28, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 28, 2020 |
| Entity Registrant Name | Bankwell Financial Group, Inc. |
| Entity Incorporation, State | CT |
| Entity File Number | 001-36448 |
| Entity Tax Identification Number | 20-8251355 |
| Entity Address, Street Name | 220 Elm Street |
| Entity Address, City | New Canaan |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06840 |
| City Area Code | 203 |
| Local Phone Number | 652-0166 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of Each Class | Common Stock, no par value pershare |
| Trading Symbol(s) | BWFG |
| Name of Each Exchange on Which Registered | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001505732 |
| Amendment Flag | false |
