Auction Rate Securities - Significant Assumptions Used to Determine Fair Value of Auction Rate Securities (Details)	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Oct. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Libor plus stated yield	2.00%	2.00%
Yields	2.15%	2.15%
Minimum
Schedule of Available-for-sale Securities [Line Items]
Discount rates	0.53%	0.42%
Average expected lives	4 years	4 years
Maximum
Schedule of Available-for-sale Securities [Line Items]
Discount rates	1.18%	0.79%
Average expected lives	10 years	10 years