I have read through FAS 141 and 142, but I can't seem to find an answer to this:
If a company acquires another company with 4 reporting units, can those reporting units and their goodwill be combined into a single goodwill account, such as "enterprise goodwill"? Also, once goodwill is impaired, what is the account method used once impairment no longer exists? Will the goodwill remain at the impaired level, and any recovery of impairment is not recognized?
Thanks for any help.

It would depend on how they were acquired. Are they acquired as separate entities (i.e. corporations, subsidiaries) or absorbed by one company LLC?

They are 4 separate reporting units within one company being acquired by one company.

I would leave them at the unit level and let them roll up into the consolidated reporting. This is because it show a clearer pic of the financials for each unit