This paper shows that the left-invariant geodesic flow on the symplectic
group relative to the Frobenius metric is an integrable system that is not
contained in the Mishchenko-Fomenko class of rigid body metrics. This system
may be expressed as a flow on symmetric matrices and is bi-Hamiltonian. This
analysis is extended to cover flows on symmetric matrices when an isomorphism
with the symplectic Lie algebra does not hold. The two Poisson structures
associated with this system, including an analysis of its Casimirs, are
completely analyzed. Since the system integrals are not generated by its
Casimirs it is shown that the nature of integrability is fundamentally
different from that exhibited in the Mischenko-Fomenko setting.