Supplemental Quarterly Financial Data (Unaudited) (Quarterly Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Quarterly Financial Data
Net sales	$ 565,447	$ 524,284	$ 482,467	$ 429,042	$ 558,365	$ 483,759	$ 485,513	$ 408,339	$ 2,001,240	$ 1,935,976	$ 1,865,627
Gross margin	167,673	151,713	142,439	113,576	169,249	134,277	137,413	118,766
Earnings before income taxes	75,076	62,468	56,756	32,944	75,201	35,497	50,336	38,537	227,244	199,571	197,807
Net Earnings:
Net earnings	$ 51,662	$ 46,001	$ 44,798	$ 23,383	$ 52,465	$ 23,663	$ 42,446	$ 27,368	$ 165,844	$ 145,942	$ 141,589
Earnings per share:
Basic earnings per share	$ 0.79	$ 0.70	$ 0.67	$ 0.35	$ 0.77	$ 0.35	$ 0.62	$ 0.40	$ 2.50	$ 2.13	$ 2.06
Diluted earnings per share	$ 0.77	$ 0.69	$ 0.66	$ 0.34	$ 0.76	$ 0.34	$ 0.61	$ 0.39	$ 2.45	$ 2.10	$ 2.01
Cash dividends per share	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.32	$ 0.32	$ 0.31