Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Net sales	$ 890,565	$ 825,962	$ 2,716,434	$ 2,461,553
Operating costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown separately below)	663,800	618,602	2,018,732	1,858,600
Selling, general and administrative	57,794	57,494	175,947	178,714
Depreciation and amortization	32,331	30,131	96,144	89,064
Acquisition and integration expenses	250	2,095	2,227	3,699
Early retirement incentives	2,030	0	5,137	0
Operating expenses	756,205	708,322	2,298,187	2,130,077
Operating income	134,360	117,640	418,247	331,476
Interest expense and other	16,768	14,543	50,668	58,676
Income from continuing operations before income taxes	117,592	103,097	367,579	272,800
Income tax expense	42,369	37,194	135,834	97,429
Income from continuing operations	75,223	65,903	231,745	175,371
Loss from discontinued operations, net	0	0	0	(765)
Net income	$ 75,223	$ 65,903	$ 231,745	$ 174,606
Earnings per share-basic:
Income from continuing operations (in dollars per share)	$ 1.51	$ 1.35	$ 4.67	$ 3.602
Loss from discontinued operations, net (in dollars per share)	$ 0.00	$ 0.00	$ 0.00	$ (0.016)
Net income (in dollars per share)	$ 1.51	$ 1.35	$ 4.67	$ 3.59
Weighted-average common shares outstanding-basic (in shares)	49,750	48,912	49,608	48,692
Earnings per share-diluted:
Income from continuing operations (in dollars per share)	$ 1.43	$ 1.27	$ 4.43	$ 3.393
Loss from discontinued operations, net (in dollars per share)	$ 0.00	$ 0.00	$ 0.00	$ (0.01)
Net income (in dollars per share)	$ 1.43	$ 1.27	$ 4.43	$ 3.38
Weighted-average common shares outstanding-diluted (in shares)	52,464	51,968	52,343	51,689
Dividends declared and paid per common share (in dollars per share)	$ 0.04	$ 0.04	$ 0.12	$ 0.10