Conversation Piece

Get them talking, and it isn't long before Brian Koppelman and David Levien are finishing each other's sentences.

But that's not unusual. After all, as Koppelman puts it, they're still in the middle of a conversation that began more than 35 years ago.

The Long Island natives met as high school students on a summer bus trip across the American West, where they bonded over a shared affinity for the same types of books, movies and TV shows.

When they returned home, they stayed in touch, and in the years that followed, Koppelman says, "We would go out and explore the culture and then report back to each other — and for kids, in a shockingly deliberate way. I remember David seeing Angel Heart and calling me in college, saying, 'I saw this movie, and I want to see it a second time so we can talk about it."

Today, Koppelman and Levien don't just consume pop culture, they create it. They first made their mark with the screenplay for the 1998 film Rounders, a pulpy blend of underground poker with undertones of existentialism, starring Matt Damon and Edward Norton.

Their résumé since then includes such features as Runaway Jury and Ocean's Thirteen and such television series as The Girlfriend Experience and, most recently, the Showtime drama Billions, which they created with financial journalist Andrew Ross Sorkin.

Pulsing with operatic themes of wealth, greed, power, loyalty, betrayal and revenge, Billions chronicles the fluid morality and shifting allegiances of Bobby "Axe" Axelrod (Damian Lewis), a swaggering New York hedge-fund titan who prefers heavy-metal T-shirts to hand-tailored suits, and Chuck Rhoades (Paul Giamatti), the congenitally indignant U.S. attorney with an Ahab-like obsession to nab Axe for a tickertape of financial improprieties.

In an intriguing twist, their mongoose-cobra pas de deux was placed on hold in the final episode of season three when the longtime adversaries forged an unlikely alliance to settle other, more urgent scores. This pause set up all manner of machinations in season four, which premiered on March 17.

In addition to their partnership as writer-producer-directors, Koppelman and Levien maintain thriving solo pursuits.

Levien, who had begun writing fiction before he and Koppelman teamed up for Rounders, has published six novels, including four unflinching crime thrillers centered around Frank Behr, an Indianapolis detective with a fragile heart and a haunted past. The latest, Signature Kill, was published to strong reviews in 2015.

Koppelman garnered media attention in 2013 with his "Six-Second Screenwriting Lessons" for aspiring writers, which he posted on the short-form video platform Vine. He ultimately recorded more than 300 of them and has racked up more than 60 million views.

He established a pithy, at times prickly, tone in the first installment when he declared, "All screenwriting books are bullshit. All. Watch movies. Read screenplays. Let them be your guide."

A year later, he launched The Moment with Brian Koppelman, a podcast in which he talks to writers, performers, entrepreneurs and other creative professionals, with an emphasis on inflection points — pivotal moments that test character and can alter life trajectories.

Both men agree that, rather than deflecting focus from their collaborative work, these individual endeavors sharpen it. "Our outside things have never threatened what we do together," Levien says. "They have always been additive."

"The central work that we do as a team flows from all of these pursuits," Koppelman adds. "The conversations I get to have on the podcast are a way to feed my insatiable curiosity about the world. Inevitably, there are things that I pick up in those conversations.

"Someone will mention a book, I'll read it, I'll send it to David, we'll talk about it and that finds its way into whatever we're doing together. The same thing will happen with something David discovers in his research for one of his novels. We're always talking about this stuff to each other."

The result of this ongoing dialogue, when they reconvene, is an almost seamless narrative alchemy, suggestive of a Vulcan mind meld.

"Billions might be the best synthesis so far, because it's such a shared vision," Levien says.

"When we outline an episode that we're going to write together, and we split up the scenes and write them separately, what happens over and over, weirdly, is when the documents are combined, everything flows together as if one person wrote it. It's the right length, the transitions make sense, sometimes we even use the same reference. Very little has to be done to make it a unified document."

Not surprisingly, this same unity extends to the set. David Costabile, who plays Mike "Wags" Wagner, Axelrod's hedonistic right-hand man, recalls an experience while shooting the 2009 film Solitary Man, which Koppelman and Levien co-directed, and in which he had a supporting role.

"I needed to ask a question, and I knew Brian better than I knew David, but David was there at the time," Costabile says. "So I asked him the question, and he gave me the exact kind of answer that Brian would have given me. And I remember thinking, 'Wow, they actually speak with the same voice. There isn't any real separation.'"

Of course, in a sense, Koppelman and Levien have not been separated — even when they've been apart — since that high school bus trip.

"We're fiercely loyal to one another," Koppelman says, "and the idea of always protecting the other guy started long before either of us had a career. It started when we were kids, and someone would come up to me or to David and be like, 'Lose the other dude and come hang.' And somehow, from the beginning, we were like, 'There is no other dude — there's just us.'"