Credit Suisse Group AG pleaded guilty Monday to criminal charges that the bank helped customers avoid paying U.S. taxes. The Department of Justice charged the Switzerland-based bank with helping thousands of Americans to avoid paying taxes with offshore accounts. The U.S. and the bank reached a plea deal in which Credit Suisse agreed to pay $2.6 billion in penalties and hire an independent monitor that will oversee it for up to two years. It is the first time in more than two decades that a major bank has pleaded guilty to U.S. federal criminal charges. The plea deal is a major blow to overseas tax dodging and marks a new aggressiveness on the part of federal prosecutors. Credit Suisse may be only the first among several banks to plead guilty to the feds. France’s BNP Paribas is expected to do the same in a few weeks.