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What are some ways to encourage team members to contribute and maintain a centralized wiki?

I joined my current company and department a few years ago. We had some documentation for processes but most people had been around for a long time and never needed it, so it was very sparse. 

Since we had access to Confluence (an internal documentation / wiki platform), whenever I learned a new process I took notes and added documentation. This has been a huge resource in training new hires, as they no longer have to create this reference information themselves. My management fully supports and encourages it; it has reduced errors and been helpful in audits as well. 

However, I am the only one who makes any significant effort to keep the information up-to-date and expand it. Some of the processes I'm no longer responsible for, but the team members currently doing them don't update the wiki to reflect changes. Others will happily use the documents I've created, but don't want to post documentation of the processes they currently own - they don't think it's good enough. 

How do I encourage a community mindset in my team where the wiki is not just viewed as "Sigma's project" but as something everyone contributes to and benefits from? I have a good rapport with my team and the support of management (though I'm looking for a more indirect approach).