Humana has left the insurance organization America's Health Insurance Plans.
Humana has not actively participated in AHIP since early 2017, according to spokesman Alex Kepnes.
"Our focus continues to be on improving the healthcare of the millions of Americans we serve through our growing clinical platform and deeper integration with doctors and other healthcare professionals," he said.
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The formal date of termination was Dec. 31, 2017.
AHIP said Humana's decision to leave was communicated to them as a business decision, rather than being related to policy, according to spokeswoman Kristine Grow.
In January 2016, Aetna said it would leave AHIP, months after the nation's largest insurer, UnitedHealthcare, part of UnitedHealth Group, left the industry's trade association.
Another of the nation's large insurers, Anthem, remained active in the organization in 2017, with CEO Joe Swedish last year serving as chairman of the board of AHIP.
"We remain a very strong organization," Grow said. "We went from a $2.3 million loss in 2015 to a $1.2 million gain in 2016."
AHIP added 12 new members last year, she said, including WellCare Health Plans and Sutter Health, two large insurers.
Humana is one of the top Medicare Advantage insurers in the country. Analysts speculate it may be ready for another takeover bid after Aetna failed last year to buy Humana and is now in talks to merge with CVS.
In November, Humana sold its commercial long-term care insurance business, KMG America Corporation, but said it would record a net loss of $400 million in the deal.
It also cut its workforce by 5.7 percent, or 2,700 employees, as third-quarter earnings showed profits dropping by 11 percent.
In December, Humana said it would acquire a 40 percent minority interest in Kindred at Home, a homecare business, in a move that provided a 65 percent overlap with its MA business and signaled another expansion by an insurer into the provider market. It made the $800 million purchase through a joint venture with two private equity firms.