"Too-big-to-fail" legislation unveiled yesterday is needed to rein in the biggest U.S. banks because the Dodd-Frank Act has failed to guard taxpayers against future bailouts, the bill’s sponsors said, Bloomberg News reported yesterday. The four largest banks—JPMorgan Chase & Co., Bank of America Corp., Citigroup Inc. and Wells Fargo & Co.—"are nearly $2 trillion larger than they were" before getting U.S. aid to help them weather the 2008 credit crisis, Sen. Sherrod Brown (D-Ohio) said yesterday. Sen. David Vitter (R-La.), whose plan is opposed by key lawmakers, proposes a 15 percent capital requirement for megabanks as a way to reduce risk and remove the perception that they would get bailouts in a crisis. Mid-size and regional banks, those between $50 billion and $500 billion in assets, would need to have 8 percent capital relative to assets.