Assembly Speaker Sheldon Silver, who bent state government to his will for more than 20 years as one of New York's most powerful and canny politicians, was arrested Thursday on charges of taking nearly $4 million in payoffs and kickbacks. The 70-year-old Democrat was taken into custody by the FBI on federal conspiracy and bribery charges that carry up to 100 years in prison and could cost him his political seat. He was released on $200,000 bail.