Earnings Per Share - Additional Information (Detail) - shares	9 Months Ended	141 Months Ended
	Jul. 31, 2016	Jul. 31, 2016	Apr. 30, 2016
Class of Stock [Line Items]
Number of shares authorized to be purchased (shares)	4,000,000	4,000,000
Repurchase of common stock (shares)		0
Shares repurchased of common stock (shares)	3,294,513	3,294,513
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.
Shares repurchased of common stock (shares)	1,425,452	1,425,452
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.
Number of shares authorized to be purchased (shares)			110,241
Shares repurchased of common stock (shares)	1,869,061	1,869,061