21st Century ( TW) surged 27% after insurance giant American International Group ( AIG) offered to buy the shares of the car insurer it doesn't already own. AIG is offering to pay $690 million, or $19.75 a share, for the company. 21st Century shares were up $4.42 to $21.01. AIG was slipping 89 cents, or 1.3%, to $68.99. National City ( NCC) rose after the Cleveland-based bank says it will buyback 75 million shares at prices ranging between $35 and $38.75. Shares were up 89 cents, or 2.4%, to $37.65. Cohen & Steers ( CNS) gained after reporting that its fourth-quarter profit nearly doubled. The asset manager earned $16.6 million, or 40 cents a share, topping the Thomson Financial consensus estimate by a nickel. Revenue rose 54% more to $57.6 million. Shares were climbing $2.49, or 5.4%, to $48.32. Charles Schwab ( SCHW) fell after the broker announced that Chief Financial Officer Christopher Dodds will retire on May 18. Replacing him will be Joseph Martinetto, the firm's current senior VP and treasurer. Shares were losing 39 cents, or 2.1%, to $18.52. Triad Guaranty ( TGIC) got pummeled after the mortgage insurer said it earned $8.1 million, or 54 cents a share, which was well below analyst expectation. Wall Street was looking for $1.32 a share. Last year Triad had a profit of $12.6 million, or 85 cents a share. The North Carolina-based company was falling $5.90, or 10%, to $52.55.