| Document and Entity Information | Apr. 24, 2020 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | IBERIABANK CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0000933141 |
| Document Type | 8-K |
| Document Period End Date | Apr. 24, 2020 |
| Entity Incorporation State Country Code | LA |
| Entity File Number | 001-37532 |
| Entity Tax Identification Number | 72-1280718 |
| Entity Address, Address Line One | 200 West Congress Street |
| Entity Address, City or Town | Lafayette |
| Entity Address, State or Province | LA |
| Entity Address, Postal Zip Code | 70501 |
| City Area Code | (337) |
| Local Phone Number | 521-4003 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock (par value $1.00 per share) |
| Trading Symbol | IBKC |
| Security Exchange Name | NASDAQ |
| Series B Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares, Each Representing a 1/400th Interest in a Share of 6.625% Perpetual Preferred Stock, Series B |
| Trading Symbol | IBKCP |
| Security Exchange Name | NASDAQ |
| Series C Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares, Each Representing a 1/400th Interest in a Share of 6.60% Perpetual Preferred Stock, Series C |
| Trading Symbol | IBKCO |
| Security Exchange Name | NASDAQ |
| Series D Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares, Each Representing a 1/400th Interest in a Share of 6.100% Perpetual Preferred Stock, Series D |
| Trading Symbol | IBKCN |
| Security Exchange Name | NASDAQ |
