When someone does more than they’re required to, that means they have ‘gone the extra mile’. A person makes special efforts when they ‘go the extra mile’ in order to achieve something. This idiom can be commonly heard in both social and professional situations. Another similar idiom is to ‘go above and beyond’. Both are common and both have very similar meanings.
Gary is a great friend. If I'm ever in any kind of trouble, I can always rely on him to go the extra mile to help me out.
One of Claire's best qualities is her willingness to go the extra mile to make sure a task is done right, even though that often means she works much longer hours than other staff members.