Betterment LLC founder and CEO Jon Stein is stepping down from his role, the company said Dec. 8.

Stein's departure from the company was a personal decision aimed at handing over the leadership role to someone who could lead Betterment in the next phase of its growth, Stein said in a separate blog post.

Former Viacom Media Networks COO Sarah Kirshbaum Levy will take over the post, while Stein will remain with the company as chairman of the board. Levy has been with Betterment as an operating adviser for the last several months.

Stein will continue as CEO through the end of December for a smooth transition.