Auction Rate Securities - Significant Assumptions Used to Determine Fair Value of Auction Rate Securities (Details)	6 Months Ended	12 Months Ended
	Apr. 30, 2017	Oct. 31, 2016
Schedule of Available-for-sale Securities
Libor plus stated yield	2.00%	2.00%
Yields	2.15%	2.15%
Minimum
Schedule of Available-for-sale Securities
Discount rates	0.38%	0.46%
Average expected lives	4 years	4 years
Maximum
Schedule of Available-for-sale Securities
Discount rates	1.00%	1.30%
Average expected lives	10 years	10 years