Fair Value Measurements (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Assets:
U.S. government obligations	$ 327,479
Fair value, Measurements, Recurring
Assets:
Money market funds	476,187	$ 511,355
U.S. government obligations	297,585	298,976
Commercial paper	99,745	89,865
Foreign currency forward contracts	97	227
Forward starting interest rate swaps	6,333	218
Total assets measured at fair value	879,947	900,641
Liabilities:
Foreign currency forward contracts	1,317	2,129
Total liabilities measured at fair value	1,317	2,129
Fair value, Measurements, Recurring | Level 1
Assets:
Money market funds	476,187	511,355
U.S. government obligations	0	0
Commercial paper	0	0
Foreign currency forward contracts	0	0
Forward starting interest rate swaps	0	0
Total assets measured at fair value	476,187	511,355
Liabilities:
Foreign currency forward contracts	0	0
Total liabilities measured at fair value	0	0
Fair value, Measurements, Recurring | Level 2
Assets:
Money market funds	0	0
U.S. government obligations	297,585	298,976
Commercial paper	99,745	89,865
Foreign currency forward contracts	97	227
Forward starting interest rate swaps	6,333	218
Total assets measured at fair value	403,760	389,286
Liabilities:
Foreign currency forward contracts	1,317	2,129
Total liabilities measured at fair value	$ 1,317	$ 2,129