Income Taxes (Tables)

12 Months Ended

Apr. 30, 2012

Income Taxes [Abstract]

Components Of Income Tax Expense Attributable To Earnings

		Years ended April 30,
		2012		2011		2010
Current tax expense
Federal	$	9,937	$	(6,171)	$	41,632
State		2,345		1,871		4,794
		12,282		(4,300)		46,426
Deferred tax expense		54,442		60,914		18,194
Total income tax provision	$	66,724	$	56,614	$	64,620

Schedule of Deferred Tax Assets and Liabilities

		As of April 30,
		2012		2011		2010
Deferred tax assets
Accrued liabilities	$	13,143	$	10,405	$	9,417
Deferred compensation		5,663		5,325		4,941
Other		7,644		5,562		3,759
Total gross deferred tax assets		26,450		21,292		18,117
Deferred tax liabilities
Excess of tax over book
depreciation		(264,757)		(211,415)		(145,433)
Other		(8,955)		(2,550)		(4,496)
Total gross deferred tax
liabilities		(273,712)		(213,965)		(149,929)
Net deferred tax liability	$	(247,262)	$	(192,673)	$	(131,812)

Schedule of Effective Income Tax Rate Reconciliation

	Years ended April 30,
	2012	2011	2010
Income taxes at the statutory rates	35.0%	35.0%	35.0%
Federal tax credits	-2.1	-1.2	-0.8
State income taxes, net of federal tax
benefit	2.9	2.9	2.1
Other	0.6	0.7	-0.7
	36.4%	37.4%	35.6%

Reconciliation Of Unrecognized Tax Benefits

		2012		2011
Beginning balance	$	6,148	$	5,482
Additions based on tax positions related to current year		2,706		1,982
Additions for tax positions of prior years		142		48
Reductions for tax positions of prior years		(47)		(192)
Reductions due to lapse of applicable statute of limitations		(1,411)		(1,172)
Settlements		-		-
Ending balance	$	7,538	$	6,148