Earnings Per Share - Additional Information (Detail) - shares	6 Months Ended	12 Months Ended
	Apr. 30, 2018	Oct. 31, 2017
Class A Common Stock
Class of Stock [Line Items]
Percentage of shares outstanding used in two class method calculation	40.00%
Voting rights	The Class A Common Stock has no voting rights unless four quarterly cumulative dividends upon the Class A Common Stock are in arrears.
Class B Common Stock
Class of Stock [Line Items]
Percentage of shares outstanding used in two class method calculation	60.00%
Voting rights	The Class B Common Stock has full voting rights.
Board Of Director Authorized
Class of Stock [Line Items]
Number of shares authorized to be purchased (shares)	4,703,487
Stock Repurchase Committee Authorized
Class of Stock [Line Items]
Repurchase of common stock (shares)	0	2,000