how can we say apple has 100bn$ cash?

all on news hear apple has 100 billion dollars of cash how can know that? businesweek's sources show balance sheet of apple , cash+cash equivalents show 10 billion dollars. can explain this? here balance sheet:

http://investing.businessweek.com/r...dataset=balancesheet&period=a&currency=native

 

i'm guessing because money offshore.

 

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