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, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
Class A Common Stock
Class of Stock [Line Items]
Basic (shares)	25,835,281	25,834,636	25,824,194	25,787,769	25,781,791	25,781,146	25,761,733	25,697,512	25,820,470	25,755,545	25,668,204
Assumed conversion of stock options and unvested shares (shares)									2,470	1,348	5,901
Diluted (shares)	25,835,281	25,835,294	25,828,882	25,792,441	25,785,266	25,783,184	25,766,609	25,704,023	25,822,940	25,756,893	25,674,105
Class B Common Stock
Class of Stock [Line Items]
Basic (shares)	22,007,725	22,009,596	22,009,725	22,009,725	22,009,725	22,009,725	22,108,942	22,119,966	22,000,000	22,100,000	22,100,000
Diluted (shares)	22,007,725	22,009,596	22,009,725	22,009,725	22,009,725	22,009,725	22,108,942	22,119,966	22,000,000	22,100,000	22,100,000
Basic and diluted shares (shares)									22,009,193	22,062,089	22,119,966