Quarterly Results (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Gross profit	$ 239,039	$ 200,428	$ 194,195	$ 204,797	$ 195,646	$ 185,488	$ 196,703	$ 221,457	$ 838,459	$ 799,294	$ 881,251
Quarterly Financial Information Disclosure [Abstract]
Net sales	430,144	416,047	383,298	352,134	338,911	329,156	340,602	374,507	1,581,623	1,383,176	1,487,205
Gross profit	239,039	200,428	194,195	204,797	195,646	185,488	196,703	221,457	838,459	799,294	881,251
Operating income	56,713	17,413	8,094	96,333	93,909	88,127	97,620	116,860	178,553	396,516	474,183
Net income from continuing operations									127,389	336,705	429,167
Net loss from discontinued operations									0	0	(10,217)
Net income	59,690	10,173	(21,184)	78,710	80,636	77,489	79,287	99,293	127,389	336,705	418,950
Diluted net income per common share - continuing operations									$ 0.62	$ 1.65	$ 2.20
Diluted net loss per common share - discontinued operations									$ 0.00	$ 0.00	$ (0.05)
Diluted net income per common share	$ 0.28	$ 0.05	$ (0.10)	$ 0.39	$ 0.39	$ 0.38	$ 0.40	$ 0.49	$ 0.62	$ 1.65	$ 2.15
Scenario, Previously Reported [Member]
Gross profit				203,079	193,873	183,779	194,994	219,748		792,394
Quarterly Financial Information Disclosure [Abstract]
Gross profit				203,079	193,873	183,779	194,994	219,748		792,394
Restatement Adjustment [Member]
Gross profit				1,718	1,773	1,709	1,709	1,709		6,900
Quarterly Financial Information Disclosure [Abstract]
Gross profit				$ 1,718	$ 1,773	$ 1,709	$ 1,709	$ 1,709		$ 6,900