Related Party Transaction - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended	0 Months Ended	1 Months Ended
Apr. 30, 2014	Apr. 30, 2013	Jan. 18, 2010 Director	Aug. 31, 2011 Director
Related Party Transaction [Line Items]
Related party transaction, compensation for tax associated with option granted				$ 0.4
Related party transaction, stock options granted	2,092,000	5,053,000	274,993

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration