A company should pay the sick leave specified in the employee handbook.
When that's gone, LTD (Long Term Disability Insurance) should kick in. This usually provides 70% of base pay up to the end of Year 2 of continuing disability, followed by 60% of base pay up to retirement age. That's how it worked at every company, large and small, that employed me.
The catch is that, at some companies, it is necessary to sign up for LTD, just like contributory group life insurance.
Good answer!