  We report on a detailed investigation of the gamma-ray emission from 18 broad
line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope
(LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111
in the GeV photon energy range; a detailed look at the temporal characteristics
of the observed gamma-ray emission reveals in addition possible flux
variability in both sources. No statistically significant gamma-ray detection
of the other BLRGs was however found in the considered dataset. Though the
sample size studied is small, what appears to differentiate 3C 111 and 3C 120
from the BLRGs not yet detected in gamma-rays is the particularly strong
nuclear radio flux. This finding, together with the indications of the
gamma-ray flux variability and a number of other arguments presented, indicate
that the GeV emission of BLRGs is most likely dominated by the beamed radiation
of relativistic jets observed at intermediate viewing angles. In this paper we
also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies,
which can be considered radio-quiet counterparts of BLRGs, and found none were
detected in gamma-rays. A simple phenomenological hybrid model applied for the
broad-band emission of the discussed radio-loud and radio-quiet type 1 active
galaxies suggests that the relative contribution of the nuclear jets to the
accreting matter is > 1 percent on average for BLRGs, whilst <0.1 percent for
Seyfert 1 galaxies.
