President Donald Trump has said he wants to roll back much of the Dodd-Frank financial reform law that Congress passed after the financial crisis. Smaller regional banks have honed in on one part of Dodd-Frank they would like to change: the rule on how big a bank has to be for it to be considered systemically important. In other words, too big to fail. It’s a topic Janet Yellen was asked about during her testimony this week on Capitol Hill and a debate that’s gaining strength in Washington.