Stockholders' Equity - Summary of Restricted Stock, Restricted Stock Unit and Performance Stock Unit Activity (Parenthetical) (Detail) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2013
Class A Common Stock [Member]
Schedule Of Restricted Stock Restricted Stock Unit And Performance Stock Unit Activity [Line Items]
Common stock additional issue	356
Performance Stock Units [Member]
Schedule Of Restricted Stock Restricted Stock Unit And Performance Stock Unit Activity [Line Items]
Performance stock units, percentage of attainment level	100.00%