Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jul. 31, 2014
Assets:
U.S. government obligations	$ 185,269
Fair Value, Measurements, Recurring | Total
Assets:
Money market funds	390,006
U.S. government obligations	155,271
Commercial paper	79,993
Foreign currency forward contracts	849
Total assets measured at fair value	626,119
Liabilities:
Foreign currency forward contracts	390
Total liabilities measured at fair value	390
Fair Value, Measurements, Recurring | Level 1
Assets:
Money market funds	390,006
U.S. government obligations	0
Commercial paper	0
Foreign currency forward contracts	0
Total assets measured at fair value	390,006
Liabilities:
Foreign currency forward contracts	0
Total liabilities measured at fair value	0
Fair Value, Measurements, Recurring | Level 2
Assets:
Money market funds	0
U.S. government obligations	155,271
Commercial paper	79,993
Foreign currency forward contracts	849
Total assets measured at fair value	236,113
Liabilities:
Foreign currency forward contracts	390
Total liabilities measured at fair value	390
Fair Value, Measurements, Recurring | Level 3
Assets:
Money market funds	0
U.S. government obligations	0
Commercial paper	0
Foreign currency forward contracts	0
Total assets measured at fair value	0
Liabilities:
Foreign currency forward contracts	0
Total liabilities measured at fair value	0
Reconciliation of changes in Level 3 fair value measurements
Balance at October 31, 2013	2,740
Issuances	0
Settlements	0
Changes in unrealized gain (loss)	(2,740)
Transfers into Level 3	0
Transfers out of Level 3	0
Balance at July 31, 2014	$ 0