  We report the analysis of Fermi Large Area Telescope data from five years of
observations of the broad line radio galaxy 3C 120. The accumulation of larger
data set results in the detection of high-energy $\gamma$-rays up to 10 GeV,
with a detection significance of about $8.7\sigma$. A power-law spectrum with a
photon index of $2.72\pm0.1$ and integrated flux of
$F_{\gamma}=(2.35\pm0.5)\times10^{-8}\:\mathrm{photon\:cm}^{-2}s^{-1}$ above
100 MeV well describe the data averaged over five year observations. The
variability analysis of the light curve with 180-, and 365- day bins reveals
flux increase (nearly twice from its average level) during the last year of
observation. This variability on month timescales indicates the compactness of
the emitting region. The $\gamma$-ray spectrum can be described as synchrotron
self-Compton (SSC) emission from the electron population producing the
radio-to-X-ray emission in the jet. The required electron energy density
exceeds the one of magnetic field only by a factor of 2 meaning no significant
deviation from equipartition.
