Fair Value Measurements (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Oct. 31, 2017
Assets:
U.S. government obligations	$ 337,894
Fair value, Measurements, Recurring
Assets:
Money market funds	521,698	$ 511,355
U.S. government obligations	298,025	298,976
Commercial paper	69,810	89,865
Foreign currency forward contracts	3,730	227
Forward starting interest rate swaps	4,117	218
Total assets measured at fair value	897,380	900,641
Liabilities:
Foreign currency forward contracts	2,415	2,129
Total liabilities measured at fair value	2,415	2,129
Fair value, Measurements, Recurring | Level 1
Assets:
Money market funds	521,698	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	521,698	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	298,025	298,976
Commercial paper	69,810	89,865
Foreign currency forward contracts	3,730	227
Forward starting interest rate swaps	4,117	218
Total assets measured at fair value	375,682	389,286
Liabilities:
Foreign currency forward contracts	2,415	2,129
Total liabilities measured at fair value	2,415	2,129
Fair value, Measurements, Recurring | Level 3
Assets:
Money market funds	0	0
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	0	0
Liabilities:
Foreign currency forward contracts	0	0
Total liabilities measured at fair value	$ 0	$ 0