Electrical problem - 86 Bronco 2

1986 bronco 2 - 4 x 4, 280,000 miles. Original motor. Everything works on this baby, however last week while driving, the entire electrical system seems to have shut off. No lights, no blinkers, no console or gauges worked. However, the vehicle kept going for the next two miles, till I drove into the yard, where it went dead. Tried turning it over. No power at all. After sitting for two hours, I turned it over and it started immediately, and have had no problem since.