'Whether or not there a separate disclosure about a specific transaction (including its price and form of consideration) depends on the size of the acquisition relative to the size of the company and whether the acquisition is "material." Accounting rules define "materiality" in an intentionally broad way. From FASB Statement of Concepts #2:
The omission or misstatement of an item in a financial report is material if, in the light of surrounding circumstances, the magnitude of the item is such that it is probable that the judgment of a reasonable person relying upon the report would have been changed or influenced by the inclusion or correction of the item.
In practice, a company's auditors will set a materiality threshold based on a company's revenue, assets, and net income. Thus, big companies can make small acquisitions without disclosing much.'
