Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Net sales	$ 976,358	$ 998,161	$ 980,067	$ 998,032	$ 964,230	$ 967,890	$ 937,755	$ 964,468	$ 3,952,618	$ 3,834,343	$ 3,753,498
Gross profit	483,441	498,976	487,474	494,049	475,311	481,319	467,452	473,769	1,963,940	1,897,851	1,860,172
Net earnings	$ 52,621	$ 67,919	$ 60,159	$ 42,243	$ 56,180	$ 62,463	$ 61,535	$ 54,909	$ 222,942	$ 235,087	$ 245,993
Earnings per common share
Basic (in dollars per share)	$ 0.36	$ 0.47	$ 0.41	$ 0.28	$ 0.36	$ 0.40	$ 0.39	$ 0.35	$ 1.51	$ 1.50	$ 1.54
Diluted (in dollars per share)	$ 0.36	$ 0.46	$ 0.41	$ 0.28	$ 0.36	$ 0.39	$ 0.39	$ 0.35	$ 1.50	$ 1.49	$ 1.51