One of television’s most powerful executives is signing off from his long-time network.

HBO’s Richard Plepler—who’s served the cable giant for nearly three decades, most recently as chairman and CEO—announced Thursday that he was leaving the network where he’s worked since 1992. During his regime, Plepler is credited with developing such hits as Game of Thrones, Veep, and Girls. The network also continued its awards streak during his time, winning 23 Emmys last year alone.

In a statement obtained by The Hollywood Reporter, the 59-year-old Plepler, who was recently profiled by Vanity Fair, said that “[as] hard as it is to think about leaving the company I love, and the people I love in it, it is the right time for me to do so.”

The announcement comes just as AT&T is in the final stages of its $85 billion merger with Time Warner, HBO’s parent company. At a company town meeting last summer, John Stankey, the head of the newly reorganized Warner Media, appeared with on-stage with Plepler. Stankey told employees that HBO, which has an estimated 130 million subscribers, would have to dramatically increase its output. “We need hours a day,” Stankey reportedly said. “It’s not hours a week, and it’s not hours a month. We need hours a day. You are competing with devices that sit in people’s hands that capture their attention every 15 minutes.”

Such demands would certainly have posed a challenge to Plepler and HBO’s long-standing autonomy within the corporation. The Hollywood Reporter notes that Plepler informed Stankey of his decision a few weeks ago. The publication also noted earlier this week that former NBC Entertainment head Bob Greenblatt is in talks with WarnerMedia about a major role.