It’s not often that CNN gets to boast about walloping both of its rivals in the ratings, but the venerable cable news network achieved that bragging right this weekend. There’s just one small caveat: The victory had nothing to do with news; rather, it came from “Life Itself,” a new documentary about renowned film critic Roger Ebert, which drew an audience of 506,000 viewers for its Sunday night premiere on CNN. In the same time slot, MSNBC drew 265,000 viewers, and Fox News drew 497,000 viewers, according to CNN, which cited data from Nielsen Media.

It’s a win for CNN, not so much for cable news as a sustainable business model.

“Life Itself,” which premiered at the 2014 Sundance Film Festival, marks the 16th documentary to air on CNN through its 2-year-old CNN Films division. It’s also the highest-rated so far, CNN said Monday, and the only CNN Films premiere to place No. 1 in total cable news viewers.

The movie’s success follows other huge victories for CNN Films, most notably “Blackfish,” which premiered at No. 1 in the key 25-54 demographic in October 2013. Another ratings hit for the division was the 10-episode miniseries “The Sixties,” which ran throughout the year in 2014, often pumping up CNN’s viewership during slow news periods.

All of which speaks to an obvious conclusion: As CNN continues its push into documentary programming, it is also transitioning further and further away from its old model as a pure-play news network. This, of course, will come as little surprise to anyone who has followed the channel’s mercurial travails since the former NBCUniversal phenom Jeff Zucker took over as president of CNN Worldwide January 2013. From the beginning, Zucker was meant to shake things up, and he has -- with a steady mix of hits and misses, including new offerings like the morning show “New Day” (hit) and a revamped version of “Crossfire” (miss).

But despite the programming changes, ratings have still proved elusive, particularly in primetime, where CNN hit a record low in 2014, down 9 percent to an average of 515,000 nightly viewers. And as cable news audiences continue to age, there is little evidence those trends will reverse in the years ahead. Granted, CNN has a younger audience compared to its rivals, but “young” is a relative term in cable news. As TV Newser reported last week, the median age of CNN’s viewers in 2014 was 58, compared with 61 for MSNBC and 68 for Fox News. And as Pew Research reported last year, viewership for all of cable news has been on a steady decline since the 2008 presidential election.

In the face of such murky prospects, it’s no wonder why CNN is taking every opportunity to tout its occasional ratings victories. But it’s also interesting to observe how many of those victories are non-news-related. Documentaries like “Life Itself” -- and reality series like “Anthony Bourdain: Parts Unknown” -- are a hit with viewers, but it remains to be seen if CNN will reach a saturation point where its core audience will reject its shift away from news.

Ted Turner launched CNN in 1980 with a simple mission to provide 24-hour-a-day news programming, and in 1980 that was a bold idea. Cable television was still in its infancy, and the World Wide Web was not even a glimmer in Tim Berners-Lee’s eye. But the window between cable news’ ascent and the rise of digital media was a brief one. And so CNN is reinventing itself for an era when most consumers are plugged into online news all day long. In doing so, the cable news network is conceding to the growing obsolescence of cable news.

Christopher Zara is a senior writer who covers media and culture. Got a news tip? Email me here. Follow me on Twitter @christopherzara.