A funny thing happened this week on the way to that big cable box in the sky: Three of the largest U.S. cable operators actually added subscribers.

In releasing their fourth quarter and full-year earnings for 2015, Time Warner Cable, Comcast and Charter Communications all posted subscriber gains for the past quarter. While it's common for cable operators to see a bump in subscribers at the end of the year, both Time Warner Cable and Charter–which are planning to merge–posted full year subscriber gains, ending years of declines.

Time Warner Cable added 54,000 subs in the fourth quarter after it lost more than 300,000 during the same period last year. For the full year, TWC added 32,000 subscribers, marking its first full year of growth since 2006. Charter, which released earnings this morning, had its best full year in more than a decade by adding 11,000 subscribers, including 33,000 during the fourth quarter.

Meanwhile, Comcast had its strongest fourth quarter in eight years by adding 89,000 subscribers, though it posted an overall decline in 2015 of 36,000. That is a huge improvement versus 2014, when the nation's largest carrier lost 194,000 subscribers.

The gains by the three cable operators come amidst the worst year for the overall pay-TV sector; MoffettNathanson predicted cords would be cut in 514,000 homes in 2015, down from 1.2 million in 2014.

A number of factors contributed to those expanding subscriber bases. Executives from the three companies attributed the growth to fancy new set-top boxes that offer better user experiences; an increase in the amount of "TV Everywhere" options and episodes available to watch on demand; and better marketing about bundling television and broadband services.

And it appears the slowing of cord cutting among cable operators is hurting the satellite and Telco services. Telco growth, including Verizon FiOS and AT&T U-verse, dipped from 1.06 million new subscribers in 2014 to just 118,000 in 2015. Satellite, including DirecTV and DISH, was projected to lose 560,000 subscribers for the year, more than cable.

Last week, AT&T reported a loss of 26,000 subscribers between its DirecTV and U-Verse services for the fourth quarter.