Earnings Per Share - Reconciliation of Shares Used to Calculate Basic and Diluted Earnings Per Share (Detail) - shares	3 Months Ended								12 Months Ended
	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016
Class A Common Stock
Class of Stock [Line Items]
Basic (shares)	25,941,279	25,941,279	25,934,680	25,845,758	25,835,281	25,834,636	25,824,194	25,787,769	25,915,887	25,820,470	25,755,545
Assumed conversion of stock options and unvested shares (shares)									49,969	2,470	1,348
Diluted (shares)	26,139,524	25,941,279	25,934,680	25,845,758	25,835,281	25,835,294	25,828,882	25,792,441	25,965,856	25,822,940	25,756,893
Class B Common Stock
Class of Stock [Line Items]
Basic (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,009,596	22,009,725	22,009,725	22,000,000	22,000,000	22,100,000
Diluted (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,009,596	22,009,725	22,009,725	22,000,000	22,000,000	22,100,000
Basic and diluted shares (shares)									22,007,725	22,009,193	22,062,089