The nation's four big banks saw their stocks riled by another contentious day on Wall Street Wednesday, with the Dow Jones falling more than 500 points. Bank of America (BAC) and Citigroup's (C) stock fell in the 9- to 10%-range, while JPMorgan (JPM) and Wells Fargo's (WFC) stock plummeted 5% to 7% by the close of trading. The day brought mixed news to mortgage insurers, with The PMI Group (PMI) rebounding somewhat from a rough four days in which it lost 50% of its value. As of Wednesday, the stock was back up 7%, trading at 35 cents per share after reaching a low of 25 cents last week. Insurers Genworth (GNW) and MGIC (MTG), on the other hand, saw their stock values plunge roughly 10% and 12%, respectively. Mortgage insurance firms as a whole were pummeled last week as weak economic news in the housing segment and international debt fears sent the stock market plunging. Homebuilders also were hurting as stocks turned sour but D.R. Horton (DHI) managed to close the day with a less than 5% loss, but still saw its stock hit a 52-week low at $9.14 per share before closing the day at $9.18 a share. PulteGroup (PHM) fared worse, losing more than 9% by the close,  ending the day at $4.24 after also reaching a 52-week low of $4.22 during trading Wednesday. Write to: Kerri Panchuk.