Clear Channel ( CCU) said Tuesday it will buy back up to $1 billion worth of its own stock over the next year. "This is a reflection of our Board's confidence in the Company's financial strength and our overall commitment to our shareholders," CEO Lowry Mays said. "We believe that the purchase of our common stock represents an attractive opportunity to benefit the long-term interests of the Company and its shareholders." If it used the entire buyback authority, the big San Antonio, Texas-based radio advertising firm would retire some 4% of its outstanding shares. After rising 40 cents during regular trading Tuesday, Clear Channel shares surged another 40 cents in after-hours action to $42.50.