Mike Bloomberg makes billions of dollars from Wall Street every year. But his plan to rein in the financial sector is very aggressive. If he were to become president, it would be fought vociferously by the biggest clients of Bloomberg LP, the financial-information company that's the source of the candidate's wealth. Why it matters: Bloomberg's detailed financial reform policy, released Tuesday, could cost Wall Street trillions of dollars while significantly increasing regulatory scrutiny of financial activities. It's a vision that would not be at all surprising coming from Elizabeth Warren, but that was less expected from an avatar of red-blooded capitalism.How it works: At the top of Bloomberg's wish list is for banks to hold significantly more capital on their balance sheets. While the policy doesn't specify a number, it does approvingly footnote a paper from the Minneapolis Fed that would end "too big to fail" by raising the so-called "capital requirement" for banks from 13% to as much as 38% for the biggest banks. The Minneapolis Fed plan would force the banks to raise about $2 trillion from the markets, and would raise loan rates by 1.4 percentage points. Add it all up, and the total cost is estimated by the Minneapolis Fed at about 30% of GDP. The Minneapolis Fed calculates the benefits of its plan as higher than the costs, thanks to banking crises happening much less frequently.Also on Bloomberg's list: A financial transactions tax, affecting mostly the very wealthy, that would raise about $500 billion over 10 years. Every stock, bond, and derivatives transaction would be taxed a tiny amount, helping to discourage socially-useless high-frequency trading."Speed limits" on the stock exchange that would level the playing field by allowing everybody's orders to be filled at the same time and at the same price.Allowing the Post Office to provide banking services. Tougher banking supervision, including more stringent stress tests from the Fed and a ban on banks using their money to speculate in the markets. Fully nationalize Fannie Mae and Freddie Mac.Beef up the Consumer Financial Protection Bureau.Automatically tie student loan payments to income, and make it easier to discharge student loans in bankruptcy.The bottom line: Where President Trump deregulated Wall Street, Bloomberg wants to re-regulate it — and he wants to go significantly further than even former President Obama managed with the post-crisis Dodd-Frank legislation.Go deeper: Michael Bloomberg on the issues, in under 500 words