Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013
Assets:
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	$ 15,022
Fair Value, Measurements, Recurring [Member] | Total [Member]
Assets:
Short-term investments	99,981
Prepaid expenses and other	261
Long-term Investments	15,022
Other long-term assets	2,510
Total assets measured at fair value	117,774
Liabilities:
Accrued liabilities	575
Total liabilities measured at fair value	575
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Short-term investments	99,981
Prepaid expenses and other	0
Long-term Investments	15,022
Other long-term assets	0
Total assets measured at fair value	115,003
Liabilities:
Accrued liabilities	0
Total liabilities measured at fair value	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Short-term investments	0
Prepaid expenses and other	261
Long-term Investments	0
Other long-term assets	0
Total assets measured at fair value	261
Liabilities:
Accrued liabilities	575
Total liabilities measured at fair value	575
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets:
Short-term investments	0
Prepaid expenses and other	0
Long-term Investments	0
Other long-term assets	2,510
Total assets measured at fair value	2,510
Liabilities:
Accrued liabilities	0
Total liabilities measured at fair value	$ 0