Derivative Financial Instruments (Tables)

9 Months Ended

Jan. 31, 2012

Derivative Financial Instruments [Abstract]

Fair value of derivative instruments

	January 31, 2012				April 30, 2011
	Other Current Assets		Other Current Liabilities		Other Current Assets		Other Current Liabilities		Other Noncurrent Liabilities
Derivatives designated as hedging instruments:
Commodity contracts	$	350	$	1,754	$	3,408	$	0	$	0
Interest rate contract		0		0		5,423		0		1,384
Total derivatives designated as hedging instruments	$	350	$	1,754	$	8,831	$	0	$	1,384
Derivatives not designated as hedging instruments:
Commodity contracts	$	2,223	$	2,921	$	9,887	$	5,432	$	0
Foreign currency exchange contracts		56		224		317		3,204		0
Total derivatives not designated as hedging instruments	$	2,279	$	3,145	$	10,204	$	8,636	$	0
Total derivatives instruments	$	2,629	$	4,899	$	19,035	$	8,636	$	1,384

Commodity contracts gains and losses recognized on derivatives designated as cash flow hedges

	Three Months Ended January 31,						Nine Months Ended January 31,
	2012			2011			2012			2011
(Losses) gains recognized in other comprehensive (loss) income (effective portion)	$	(681	)	$	4,788		$	(10,941	)	$	17,822
(Losses) gains reclassified from accumulated other comprehensive (loss) income to cost of products sold (effective portion)		(1,546	)		5,673			4,146			11,965
Change in accumulated other comprehensive (loss) income	$	865		$	(885	)	$	(15,087	)	$	5,857
Gains (losses) recognized in cost of products sold (ineffective portion)	$	15		$	84		$	(498	)	$	458

Interest rate contract gains and losses recognized on the derivative designated as a cash flow hedge

	Three Months Ended January 31,					Nine Months Ended January 31,
	2012			2011		2012			2011
Losses recognized in other comprehensive (loss) income (effective portion)	$	0		$	0	$	(6,192	)	$	0
Losses reclassified from accumulated other comprehensive (loss) income to interest expense (effective portion)		(130	)		0		(148	)		0
Change in accumulated other comprehensive (loss) income	$	130		$	0	$	(6,044	)	$	0
Losses recognized in interest expense (ineffective portion)	$	0		$	0	$	(19	)	$	0

Gains and losses recognized in cost of products sold on derivatives not designated as qualified hedging instruments

	Three Months Ended					Nine Months Ended
	January 31,					January 31,
	2012		2011			2012		2011
Gains (losses) on commodity contracts	$	1,008	$	(359	)	$	16,812	$	4,488
Gains (losses) on foreign currency exchange contracts		117		(863	)		1,772		(593	)
Gains (losses) recognized in cost of products sold (derivatives not designated as hedging instruments)	$	1,125	$	(1,222	)	$	18,584	$	3,895

Outstanding derivative contracts

	January 31, 2012		April 30, 2011
Commodity contracts	$	462,604	$	869,107
Foreign currency exchange contracts		74,255		73,158
Interest rate contract		0		376,000