For a system in contact with several reservoirs r at different inverse-temperatures Equation or symbol description not available, we describe how the Markov jump dynamics with the generalized detailed balance condition can be analyzed via a statistical physics approach of dynamical trajectories Equation or symbol description not available over a long time interval Equation or symbol description not available. The relevant intensive variables are the time-empirical density Equation or symbol description not available, that measures the fractions of time spent in the various configurations Equation or symbol description not available, and the time-empirical jump densities Equation or symbol description not available, that measure the frequencies of jumps from configuration Equation or symbol description not available to configuration Equation or symbol description not available when it is the reservoir r that furnishes or absorbs the corresponding energy difference (Equation or symbol description not available).