General Motors will idle three of 29 North American factories and lay off 5,200 workers next week to cut production as demand for new cars and trucks slows, Bloomberg News reported today. One plant in Canada, in Ste. Therese, Quebec, and two in the U.S., in Shreveport, Louisiana, and Wentzville, Missouri, will be idled, the company said in a statement. GM doesn't disclose how much the shutdowns will reduce production, spokesman Tom Wickham told Bloomberg.