AmericanWest Bancorporation will sell operating subsidiary AmericanWest Bank to private investors in a deal that Patrick Rusnak, company president and CEO, said Wednesday was the best possible outcome for the Spokane-based bank, its employees and customers. The holding company will file bankruptcy, he said, but AmericanWest’s 58 branches in Eastern Washington, Idaho, and Utah will remain open, with additional capital to support more lending, he said.