After 20 years at the top of Showtime Networks, Matthew Blank will pass the CEO reins to president David Nevins in January.

The executive transition at the pay cable group was announced Thursday morning by Blank at an internal company meeting in New York. Blank will remain chairman of Showtime Networks for the next few years and maintain an active exec role in guiding strategy and big-picture decisions at the company. Showtime’s senior exec staff will report to Nevins when he ascends to president-CEO on Jan. 1. After the transition, Nevins will report directly to CBS Corp. president-CEO Leslie Moonves, as well as to Blank.

The shuffle at the top of Showtime had long been expected. Nevins hit the ground running after joining the company in 2010. He’s been the clear heir apparent as he fired up the company’s original programming slate with a string of distinctive hits including “Homeland,” “Ray Donovan,” “Masters of Sex,” “Penny Dreadful” and “The Affair.”

Blank is among the TV industry’s longest-serving CEOs. He’s a pillar of New York’s television community and one of the most respected execs in the business. A true cable pioneer, Blank spent a dozen years at HBO before joining Showtime as head of marketing in 1988. He was upped to CEO in 1995.

Matt Blank has led Showtime as its chairman and CEO through two decades of dramatic change and evolution in the industry,” said Moonves. “At each and every turn, he has shown terrific instincts and knowledge of the business. His patience, energy and dedication were central to building Showtime into the powerhouse it is today. He is passing the CEO torch at a terrific time, with Showtime now poised for significant new growth over the Internet.”

Blank will continue to play a key role in guiding Showtime’s distribution strategies — a vital issue now that the company is launching a stand-alone OTT offering next month. His longstanding relationships with top execs at MVPDs will be crucial in bringing cable operators on board to promote the stand-alone service even as Showtime embraces new digital distribution partners including Apple and Roku. Blank will continue to rep Showtime on the board of the cable biz’s lobbying org, the National Cable & Telecommunications Assn.

Working with Nevins during the past five years has been “one of the great joys of my career,” Blank said.

“I know he’ll bring his great programming, business and leadership skills, as well as his passion for Showtime, to his new responsibilities. This is a time of great opportunity for the company, and we are delighted David will be at the helm,” Blank said.

Nevins made his mark early on with the first series he developed after launching Showtime, “Homeland.” The CIA thriller was a hit out of the gate and went on to win Showtime’s first Emmy Award for best drama series as well as a Peabody and other accolades. In the past few years Nevins has also focused on expanding Showtime’s slate of documentary and sports programming.

“This transition comes at a time of truly exciting growth for Showtime,” said Nevins. “I feel fortunate to be handed the reins by Leslie and Matt, who have been the kind of mentors you can only hope to find once in a lifetime. Looking forward, all of us at Showtime will benefit immeasurably from Matt’s ongoing guidance and counsel as chairman.”

Moonves said Nevins had demonstrated that he had both the programming chops and the management skills to take on the top job. Nevins came to Showtime after successful executive runs NBC, Fox and Imagine Television. At Imagine he was a driving force behind such notable series as Fox’s “24” and “Arrested Development” and NBC’s “Parenthood” and “Friday Night Lights.”

“David is quite simply one of the most brilliant creative minds in our business today, and a great business manager as well, a combination that is both rare and incredibly valuable,” Moonves said. “We couldn’t be more excited about the great skills that he brings to the job, and the incredible potential that he will be sure to realize.”

Blank spent the early years of his career criss-crossing the country to launch HBO at a time when he had to convene meetings at the local Elks Club just to explain what cable TV was to prospective customers. Showtime Networks consisted of two channels, Showtime and the Movie Channel, when Blank first joined the company. Today, it offers 27 channels, VOD and authenticated streaming services, and earlier this year the company set a deal for the launch of its first Showtime-branded international channel, with Canada’s Bell Media.

Moonves saluted Blank’s role in the growth of Showtime, and credited the exec with helping to groom Nevins as his successor.

“One of the key attributes I look for in my leadership team is the capacity and willingness to bring up the next generation of management,” Moonves said. “Matt has been an eager partner and invaluable contributor to the succession planning process at Showtime. It is a credit to Matt that we are now prepared to add the CEO duties to a talented executive like David Nevins, who is more than ready to take on this important role.”

(Pictured: Matt Blank and David Nevins)