| Document and Entity Information | Aug. 06, 2019 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | HUNTINGTON BANCSHARES INC/MD |
| Amendment Flag | false |
| Entity Central Index Key | 0000049196 |
| Document Type | 8-K |
| Document Period End Date | Aug. 6, 2019 |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 1-34073 |
| Entity Tax Identification Number | 31-0724920 |
| Entity Address, Address Line One | 41 South High Street |
| Entity Address, City or Town | Columbus |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 43287 |
| City Area Code | (614) |
| Local Phone Number | 480-2265 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| 5.875% Series C Non-Cumulative, perpetual preferred stock [Member] | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | 5.875% Series C Non-Cumulative, perpetual preferred stock |
| Trading Symbol | HBANN |
| Security Exchange Name | NASDAQ |
| 6.250% Series D Non-Cumulative, perpetual preferred stock [Member] | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | 6.250% Series D Non-Cumulative, perpetual preferred stock |
| Trading Symbol | HBANO |
| Security Exchange Name | NASDAQ |
| Common Stock—Par Value $0.01 per Share [Member] | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock—Par Value $0.01 per Share |
| Trading Symbol | HBAN |
| Security Exchange Name | NASDAQ |
