It's pretty much been this way a while now. $10B in cash. $15-20B short term securities (less than 1 year). The remainder in long term securities that mature past that 12 month mark...mostly ones that mature between 1-5 years.
So when you look on Apple balance sheet on Yahoo you see $29B "cash" (actually cash, cash equiv + short term) and $92B long term investments.
What number has been growing like crazy?
Long term: $25B in Sept 2010, $55B in Sept 2011, and $92B in Sept 2012.
But most folks count all this as "cash". These long term securities are all very safe and could be sold if necessary if Apple wanted to buy something BIG.