iHeart, formerly known as Clear Channel, is the nation’s largest radio company, with more than 850 stations. It also owns iHeartRadio’s music streaming service, a large concert business, and a 90% stake in Clear Channel Outdoor, the billboard company. Clear Channel Outdoor did not file for bankruptcy. For years, the company has been saddled with $20 billion in debt, the legacy of a leveraged buyout in 2008.