Darling not only worked hard to build the national group's infrastructure, but she brought it into the health insurance conversation in innovative ways. For instance, her Twitter account, where she has nearly 1,200 followers, has become a resource for sharing important information about healthcare reform and its impact on the business world.

"It has been a thrill to work with so many iconic, creative companies, including in the past three years, during which we have seen tectonic changes. I love this business, but I'm ready to retire from such an intense full-time job," Darling said in a statement.

Darling will serve as a senior adviser to assist with the leadership transition through the end of 2014.

Her expertise on matters related to employer health benefits has been recognized many times. In 2012, she received the Health Quality Leader Award from the National Committee for Quality Assurance. Modern Healthcare magazine included her on its list of most influential people in healthcare for the last three years, and the National Academy of Sciences in 2003 chose her as a National Associate "in recognition of her contributions to the Institute of Medicine." She also received the President's Award by the American College of Occupational and Environmental Medicine in 2010.