| Cover | Oct. 28, 2020 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 28, 2020 |
| Entity File Number | 001-38258 |
| Entity Registrant Name | Merchants Bancorp |
| Entity Central Index Key | 0001629019 |
| Entity Tax Identification Number | 20-5747400 |
| Entity Incorporation, State or Country Code | IN |
| Entity Address, Address Line One | 410 Monon Boulevard |
| Entity Address, City or Town | Carmel |
| Entity Address, State or Province | IN |
| Entity Address, Postal Zip Code | 46032 |
| City Area Code | (317) |
| Local Phone Number | 569-7420 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, without par value |
| Trading Symbol | MBIN |
| Security Exchange Name | NASDAQ |
| Series A Preferred Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A Preferred Stock, without par value |
| Trading Symbol | MBINP |
| Security Exchange Name | NASDAQ |
| Series B Preferred Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares, each representing a 1/40th interest in a share of Series B Preferred Stock, without par value |
| Trading Symbol | MBINO |
| Security Exchange Name | NASDAQ |
