| Document and Entity Information Document | Oct. 14, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 14, 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 |
