The U.S. Senate began debate on legislation combining the last pieces to the Democratic overhaul of the healthcare system and a shake-up to the student-loan industry. President Barack Obama signed into law the main healthcare bill earlier in the day. The bill was passed by the Senate on Christmas Eve and then by the House late Sunday by a thin margin. The Senate is now debating a series of corrections demanded by House lawmakers for their support of the main healthcare bill. In some cases these changes are significant, the Wall Street Journal reports.