0001195933 2017-01-01 2017-12-31 0001195933 2018-02-09 0001195933 2017-06-30 iso4217:USD xbrli:shares false --12-31 FY 2017 2017-12-31 10-K/A 0001195933 10941936 Yes Large Accelerated Filer 1007156859 INFINITY PROPERTY & CASUALTY CORP No Yes