Short-term and Long-term Investments (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Jul. 31, 2014	Oct. 31, 2013
Long Term Investments
Estimated Fair Value	$ 185,269
U.S. government obligations
Long Term Investments
Amortized Cost	155,253	114,970
Gross Unrealized Gains	42	46
Gross Unrealized Losses	(24)	0
Estimated Fair Value	155,271	115,016
Commercial paper
Long Term Investments
Amortized Cost	29,998	24,994
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	29,998	24,994
Short-term investments | U.S. government obligations
Long Term Investments
Amortized Cost	90,210	99,974
Gross Unrealized Gains	42	11
Gross Unrealized Losses	0	0
Estimated Fair Value	90,252	99,985
Short-term investments | Commercial paper
Long Term Investments
Amortized Cost	29,998	24,994
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	29,998	24,994
Other Long-term investments | U.S. government obligations
Long Term Investments
Amortized Cost	65,043	14,996
Gross Unrealized Gains	0	35
Gross Unrealized Losses	(24)	0
Estimated Fair Value	$ 65,019	$ 15,031