SELECTED CONSOLIDATING FINANCIAL STATEMENTS OF PARENT, GUARANTORS AND NON-GUARANTORS (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidating Financial Statements, Captions
Net sales	$ 967,345	$ 938,181		$ 1,911,028	$ 1,825,869
Operating costs and expenses:
Cost of sales	771,318	703,654		1,467,789	1,354,931
Selling, general and administrative	63,583	56,193		130,300	118,152
Depreciation and amortization	38,244	31,998		76,178	63,813
Relocation Charges	1,229	0		2,444	0
Acquisition and integration expenses	0	1,432		0	1,977
Defined Benefit Plan, Special Termination Benefits	0	(1,957)		0	(3,107)
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period		1,957	1,150
Total operating costs and expenses	874,374	795,234		1,676,711	1,541,980
Operating income (loss)	92,971	142,947		234,317	283,889
Intercompany interest and charges	0	0		0	0
Interest expense and other	20,321	16,668		40,031	33,900
Income (loss) from continuing operations, before income taxes	72,650	126,279		194,286	249,989
Income tax expense (benefit)	23,134	46,088		65,727	93,466
Net income	49,516	80,191		128,559	156,523
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	4,300	2,615		4,643	(3,472)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	53,816	82,806		133,202	153,051
Parent
Consolidating Financial Statements, Captions
Net sales	0	0		0	0
Operating costs and expenses:
Cost of sales	0	0		0	0
Selling, general and administrative	10,185	10,189		20,776	20,775
Depreciation and amortization	788	610		1,422	1,209
Relocation Charges	0			0
Acquisition and integration expenses		0			295
Defined Benefit Plan, Special Termination Benefits					3,107
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period		1,957
Total operating costs and expenses	10,973	12,756		22,198	25,386
Operating income (loss)	(10,973)	(12,756)		(22,198)	(25,386)
Intercompany interest and charges	(53,356)	(49,217)		(110,746)	(98,554)
Interest expense and other	19,304	15,143		37,952	30,642
Income (loss) from continuing operations, before income taxes	23,079	21,318		50,596	42,526
Income tax expense (benefit)	3,140	8,709		11,532	18,889
Net income	19,939	12,609		39,064	23,637
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	0		0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	19,939	12,609		39,064	23,637
Guarantors Subsidiaries
Consolidating Financial Statements, Captions
Net sales	924,624	914,943		1,827,850	1,777,419
Operating costs and expenses:
Cost of sales	736,898	687,053		1,404,453	1,321,190
Selling, general and administrative	46,740	41,412		97,466	87,585
Depreciation and amortization	35,429	30,282		71,061	60,415
Relocation Charges	1,229			2,444
Acquisition and integration expenses		1,432			1,682
Defined Benefit Plan, Special Termination Benefits					0
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period		0
Total operating costs and expenses	820,296	760,179		1,575,424	1,470,872
Operating income (loss)	104,328	154,764		252,426	306,547
Intercompany interest and charges	52,101	48,441		108,531	96,952
Interest expense and other	1,833	2,062		3,567	4,493
Income (loss) from continuing operations, before income taxes	50,394	104,261		140,328	205,102
Income tax expense (benefit)	19,890	37,140		53,721	73,984
Net income	30,504	67,121		86,607	131,118
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,021	(1,478)		1,873	(3,143)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	31,525	65,643		88,480	127,975
Non-Guarantor Subsidiaries
Consolidating Financial Statements, Captions
Net sales	44,080	24,274		85,721	51,175
Operating costs and expenses:
Cost of sales	35,779	17,637		65,879	36,466
Selling, general and administrative	6,658	4,592		12,058	9,792
Depreciation and amortization	2,027	1,106		3,695	2,189
Relocation Charges	0			0
Acquisition and integration expenses		0			0
Defined Benefit Plan, Special Termination Benefits					0
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period		0
Total operating costs and expenses	44,464	23,335		81,632	48,447
Operating income (loss)	(384)	939		4,089	2,728
Intercompany interest and charges	1,255	776		2,215	1,602
Interest expense and other	(816)	(537)		(1,488)	(1,235)
Income (loss) from continuing operations, before income taxes	(823)	700		3,362	2,361
Income tax expense (benefit)	104	239		474	593
Net income	(927)	461		2,888	1,768
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3,279	4,093		2,770	(329)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	2,352	4,554		5,658	1,439
Eliminations
Consolidating Financial Statements, Captions
Net sales	(1,359)	(1,036)		(2,543)	(2,725)
Operating costs and expenses:
Cost of sales	(1,359)	(1,036)		(2,543)	(2,725)
Selling, general and administrative	0	0		0	0
Depreciation and amortization	0	0			0
Relocation Charges	0			0
Acquisition and integration expenses		0			0
Defined Benefit Plan, Special Termination Benefits					0
Total operating costs and expenses	(1,359)	(1,036)		(2,543)	(2,725)
Operating income (loss)	0	0		0	0
Intercompany interest and charges	0	0		0	0
Interest expense and other	0	0		0	0
Income (loss) from continuing operations, before income taxes	0	0		0	0
Income tax expense (benefit)	0	0		0	0
Net income	0	0		0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	0		0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 0	$ 0		$ 0	$ 0