Several years ago, Billy Joel began considering something he’d long been reluctant to do: take part in a documentary about his life.

As Joel’s record-setting, 10-year residency at Madison Square Garden seemed to be reaching its peak in the pre-COVID era, "there was a couple of conversations about: Maybe now is the time to let some filmmakers in and look under the hood," said Steve Cohen, Joel’s lighting designer and creative director since 1974.

Joel’s response, according to Cohen: “‘All I really care about is that if someone tells a story, that they tell the truth.’ "

The end result of those initial conversations is "Billy Joel: And So It Goes," a two-part, five-hour documentary directed by Susan Lacy and Jessica Levin. Produced by Cohen and Lacy, among others, the documentary will likely come as a revelation even to dedicated fans of the Long Island rock icon. Spoiler warning: When the film airs on HBO July 18 and 25 at 8 p.m., viewers will hear, in unprecedented detail, about Joel’s history of suicide attempts; his relationship with his former wife and manager Elizabeth Weber; his attempts to bond with his estranged father; and how these personal experiences inspired many of Joel’s songs.

"I wouldn't say he enjoyed it, but I don’t think he hated it, either," co-director Lacy says of the singer’s experience on camera. "He said, ‘You go deep, don't you?’ " she recalls. "And I said, ‘Yeah. You have to, too.’ "

Lacy had been mulling a profile of Joel since her time at "American Masters," the PBS series she created. (Lacy signed a deal to produce documentaries for HBO in 2013.) Talks heated up in the summer of 2018, by Cohen’s recollection, when he drove from his home in East Hampton to Lacy’s home in Sag Harbor, bringing with him a laptop full of archival videos that they pored over for two hours. Separately, each fielded a call from Tom Hanks’ Playtone production company: Might they be interested in a documentary on Billy Joel?

Cohen remembers telling Lacy: "There’s something in the water here."

With Playtone on board to produce, filming took place from 2021 through 2024, according to the filmmakers. The bulk of Joel’s interviews — almost all of them at a piano — were shot at the East End homes of both Cohen and Lacy, as well as the Florida homes of both Cohen and Joel. The documentary’s opening sequence features aerial shots of Joel’s sprawling Centre Island estate.

Lacy says nearly everyone she asked, from Paul McCartney to Bruce Springsteen, agreed to sit for an interview. (The only exception: Elton John, whose relationship with Joel has long been fraught.) Also willing to show up were baggage-laden figures from Joel’s past, including ex-wives Weber and Christie Brinkley (who still weeps describing the end of their fairy-tale marriage) and Liberty DeVitto, Joel’s long-serving but summarily ousted drummer.

"It’s a long time ago now," Levin said, adding that everyone who spoke "understood that this film was a definitive portrait, and it was for posterity."

One figure the filmmakers couldn’t interview: Joel’s estranged father, Howard, who left the family when Joel was a boy. When the two reconnected — Joel was around 21, he says in the film — Howard was living in Vienna and had fathered another son, Alex, today a successful orchestra conductor. Howard Joel died in 2011.

That father-son relationship — or lack of it — may have driven Joel’s creative engine more than he cares to admit, according to Lacy. Since releasing the 1977 song "Vienna," Joel has given varying accounts of its origins, calling it a metaphor for old age or saying it was inspired by an old woman he once saw cleaning streets in the city. Lacy says it took until her very last interview with Joel "to get him to admit that ‘Vienna’ actually was about his father."

Even Cohen says he learned a few things about the man he’s known for more than 50 years. "I was there when most of these songs were written," he said. "I just did not realize the depth of it all."

In May, Joel, 76, announced he was canceling all upcoming concerts after being diagnosed with normal pressure hydrocephalus, a buildup of excess fluid in the ventricles of the brain. The condition can affect vision, balance and memory function.

Joel declined to be interviewed for this article.