I believe they are only required to disclose financials of it in their next quarterly update if the transaction has a "material" impact on the business. Which is open to a lot of interpretation but generally has come to mean that the information would have an impact on whether the average shareholder would buy or sell the stock.

This is why you see Apple buy dozens of companies quietly without disclosure all the time. Because most purchases would not really change whether the average person invests, if for no other reason than the sheer size of Apple.