Cash and Investments (Details 1) $ in Thousands	Sep. 30, 2015 USD ($)
Available-for-sale investments by contractual maturity date
Due in one year or less, Amortized Cost	$ 1,713,211
Due after one year through three years, Amortized Cost	743,948
Total, Amortized Cost	2,457,159
Due in one year or less, Estimated Fair Market Value	1,713,414
Due after one year through three years, Estimated Fair Market Value	744,193
Total, Estimated Fair Market Value	$ 2,457,607