First Republic Bank ($FRC@US) plummeted 16 percent in midday trading on Wednesday by both Fitch Ratings and S&P Global Ratings on concerns that depositors could pull their cash. Both credit ratings firms noted a large sum of deposits at First Republic that are uninsured because they are above the $250,000 FDIC limit. The San Francisco-based lender has a high concentration of deposits among clients with a high net worth in coastal markets, a characteristic that is considered a “rating weakness” in today’s environment. Fitch also placed another regional bank, PacWest Bancorp, on watch for a potential credit ratings downgrade of its own.