The Alex Gibney feature is the most watched since Spike Lee's four-part report about Hurricane Katrina in 2006.

The Walking Dead may have dominated the dial on Sunday night, but it did not stop HBO from setting a handsome record with its latest documentary premiere.

Going Clear: Scientology and the Prison of Belief, Alex Gibney's two-hour exposé on the Church of Scientology, nabbed nearly 1.7 million viewers during its premiere telecast. And while that number is sure to grow once HBO-Go plays, encores and DVR views are taken into account, it already represents the network's most watched doc premiere since Spike Lee's four-part When the Levees Broke aired in 2006. (The Hurricane Katrina feature nabbed 1.75 million viewers.)

It should be noted that Going Clear also comes shy of HBO's 2013 Beyonce doc Beyonce: Life Is but a Dream (1.8 million viewers for the premiere), though that project was, essentially, a concert special.

For a more recent comparison, Going Clear's audience also bests any individual same-day performance earned by buzzy doc miniseries The Jinx. With the latest time-shifting stats, Andrew Jarecki's six-part television event about Robert Durst has thus far averaged 3.2 million weekly viewers.

HBO became the latest cable network to nix same-day ratings reports at the top of the year in response to more and more viewers opting for delayed viewing. The pay-cable network soon will see its audience shift (and likely grow) even more when it launches its over-the-top streaming service HBO Now in April. The service will open up the network's roster of original programming, as well as its film catalog, to non-cable-subscribers for the first time.