| Document and Entity Information Document | May 07, 2020 | Feb. 06, 2020 |
| Entity Information [Line Items] | ||
| Document Type | 8-K | |
| Document Period End Date | May 7, 2020 | |
| Entity File Number | 1-11917 | |
| Entity Registrant Name | FBL Financial Group, Inc. | |
| Entity Incorporation, State or Country Code | IA | |
| Entity Tax Identification Number | 42-1411715 | |
| Entity Address, Address Line One | 5400 University Avenue, | |
| Entity Address, City or Town | West Des Moines, | |
| Entity Address, State or Province | IA | |
| Entity Address, Postal Zip Code | 50266-5997 | |
| City Area Code | (515) | |
| Local Phone Number | 225-5400 | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Title of 12(b) Security | Class A Common Stock, without par value | |
| Trading Symbol | FFG | |
| Security Exchange Name | NYSE | |
| Entity Emerging Growth Company | false | |
| Entity Central Index Key | 0001012771 | |
| Amendment Flag | false |
