CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Revenues:
Product sales	$ 541,205	$ 488,187	$ 1,090,692	$ 930,784
Product sales to related party	16,799	14,585	35,805	30,143
Commissions	5,110	4,398	9,465	8,144
Total revenues	563,114	507,170	1,135,962	969,071
Cost of product sales	488,435	440,552	984,354	839,939
Gross profit	74,679	66,618	151,608	129,132
Selling, general and administrative expenses	47,928	42,933	95,388	81,840
Depreciation and amortization	2,513	2,274	4,905	4,466
Operating income	24,238	21,411	51,315	42,826
Other income (expense):
Interest expense	(223)	(252)	(426)	(435)
Earnings of equity method investees	85	79	178	156
Other	209	186	413	374
Total other income (expense), net	71	13	165	95
Income before taxes	24,309	21,424	51,480	42,921
Income tax expense	(9,209)	(8,246)	(19,629)	(16,547)
Net income	$ 15,100	$ 13,178	$ 31,851	$ 26,374
Earnings per common share
Basic	$ 1.19	$ 1.04	$ 2.51	$ 2.09
Diluted	$ 1.19	$ 1.04	$ 2.51	$ 2.09
Weighted average common shares outstanding:
Weighted Average Number of Shares Outstanding, Basic	12,674	12,619	12,669	12,600
Weighted Average Number of Shares Outstanding, Diluted	12,709	12,648	12,702	12,626