Billy Joel is opening up about a tough moment with longtime friend and tourmate Elton John. In the second part of the new two-part HBO Documentary, "Billy Joel: And So It Goes," the "New York State of Mind" singer shared how John's public comments that he needed rehab strained their friendship.

Billy Joel acknowledged “bad blood” between himself and Elton John in the second installment of his two-part HBO documentary “Billy Joel: And So It Goes,” released Friday. Joel explained the pair’s fallout occurred after John publicly insisted he needed to go to rehab.