Document and Entity Information - shares |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Apr. 26, 2018 |
|
| Document Information [Abstract] | ||
| Document Type | 10-Q | |
| Amendment Flag | false | |
| Document Period End Date | Mar. 31, 2018 | |
| Document Fiscal Year Focus | 2018 | |
| Document Fiscal Period Focus | Q1 | |
| Entity Registrant Name | INFINITY PROPERTY & CASUALTY CORP | |
| Entity Central Index Key | 0001195933 | |
| Current Fiscal Year End Date | --12-31 | |
| Entity Filer Category | Large Accelerated Filer | |
| Entity Common Stock, Shares Outstanding | 10,941,936 |