Fair Value Measurements (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Oct. 31, 2017
Assets:
U.S. government obligations	$ 258,405
Fair value, Measurements, Recurring
Assets:
Money market funds	579,413	$ 511,355
U.S. government obligations	228,462	298,976
Commercial paper	69,860	89,865
Foreign currency forward contracts	668	227
Forward starting interest rate swaps	6,667	218
Total assets measured at fair value	885,070	900,641
Liabilities:
Foreign currency forward contracts	2,968	2,129
Total liabilities measured at fair value	2,968	2,129
Fair value, Measurements, Recurring | Level 1
Assets:
Money market funds	579,413	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	579,413	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	228,462	298,976
Commercial paper	69,860	89,865
Foreign currency forward contracts	668	227
Forward starting interest rate swaps	6,667	218
Total assets measured at fair value	305,657	389,286
Liabilities:
Foreign currency forward contracts	2,968	2,129
Total liabilities measured at fair value	$ 2,968	$ 2,129