U.S. companies are plowing a record amount of money into buying back stock

Flush with cash from President Trump’s tax overhaul and bathing in more earnings than they know what to do with, U.S. companies are embarking on a buyback binge of historic dimension.

How big will it be? JPMorgan Chase & Co. strategists led by Dubravko Lakos-Bujas estimate that gross share repurchases…