Doesn't the word "cash" imply that the money is not invested? If they bought factories or something else productive, we'd usually refer to that as "capital".
Treasuries and certain other government securities count as "cash" in most cases.
Edit: Apple reports most of the amount bandied about as their "cash" as being in "long-term marketable securities." [2]. So it's a mix that is definitely not designed to all be instantly convertible to USD with no penalty. I'd guess most other large companies manage their cash similarly.
1 - https://en.wikipedia.org/wiki/Cash_and_cash_equivalents#Comp...
2 - https://www.apple.com/newsroom/pdfs/Q2FY17ConsolidatedFinanc...