Humana holds a contract with TriCare (the military's insurance) for $45 billion and someone wants to see the contract. According to Becker's Hospital Review, Humana has filed a reverse-FOIA action to block the public from seeing details of this contract.
This is called a reverse-FOIA suit and it is what happens when a contractor doesn't want its information released under the FOIA. Usually, the contractor will say the information is trade secrets or confidential business information and should be protected pursuant to FOIA Exemption 4.
There is a long line of case law for whether something is or isn't protected under Exemption 4. Congress hasn't amended this exemption in a number of years - they did make proposals exempt under the FOIA, but that was under Exemption 3.
States often have much more liberal rules for allowing the release of final contracts than the Feds do, which means that contractors that operate under both federal and state contracts will have their information released at the state level but protected under the federal level. As it is for different contracts, this fiction that their information is never made public is allowed to live on.