Flying Assets under Capital Lease (Detail) (Flying Assets under Capital Lease, USD $) In Thousands, unless otherwise specified	Apr. 30, 2012	Apr. 30, 2011
Flying Assets under Capital Lease
Flying assets under capital lease:
Cost	$ 32,795	$ 149,653
Accumulated amortization	(2,073)	(1,745)
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Flight Equipment, Net, Total	$ 30,722	$ 147,908

The cumulative amount of depreciation that has been recognized in the income statement related to long-lived, depreciable flight assets used in the entity's principle business operations, subject to a lease and meeting the criteria for capitalization.

No definition available.

Name:	us-gaap_CapitalLeasesLesseeBalanceSheetAssetsByMajorClassFlightEquipmentAccumulatedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant