Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Quarterly Financial Data (Unaudited)
Net sales	$ 906,435	$ 912,101	$ 898,239	$ 905,441	$ 882,557	$ 886,991	$ 889,281	$ 864,815	$ 3,622,216	$ 3,523,644	$ 3,269,131
Gross profit	449,358	457,083	444,454	444,368	440,236	444,379	436,786	421,857	1,795,263	1,743,259	1,594,605
Net earnings	$ 64,812	$ 72,466	$ 64,889	$ 58,983	$ 65,630	$ 69,487	$ 67,813	$ 30,134	$ 261,151	$ 233,064	$ 213,725
Earnings per common share
Basic (in dollars per share)	$ 0.39	$ 0.43	$ 0.37	$ 0.33	$ 0.36	$ 0.38	$ 0.36	$ 0.16	$ 1.52	$ 1.27	$ 1.17
Diluted (in dollars per share)	$ 0.38	$ 0.42	$ 0.36	$ 0.32	$ 0.35	$ 0.37	$ 0.35	$ 0.16	$ 1.48	$ 1.24	$ 1.14