Supplemental Quarterly Financial Data (Unaudited) (Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Quarterly Financial Data
Net sales	$ 562,625	$ 494,810	$ 493,222	$ 487,646	$ 565,447	$ 524,284	$ 482,467	$ 429,042	$ 2,038,303	$ 2,001,240	$ 1,935,976
Gross margin	159,690	143,389	137,620	143,886	167,673	151,713	142,439	113,576
Earnings before income taxes	68,727	57,559	57,591	57,072	75,076	62,468	56,756	32,944	240,949	227,244	199,571
Net Earnings:
Net earnings	$ 50,060	$ 43,753	$ 43,855	$ 43,784	$ 51,662	$ 46,001	$ 44,798	$ 23,383	$ 181,452	$ 165,844	$ 145,942
Earnings per share:
Basic earnings per share	$ 0.79	$ 0.68	$ 0.67	$ 0.67	$ 0.79	$ 0.70	$ 0.67	$ 0.35	$ 2.81	$ 2.50	$ 2.13
Diluted earnings per share	0.77	0.66	0.66	0.66	0.77	0.69	0.66	0.34	2.75	2.45	2.10
Cash dividends per share	$ 0.10	$ 0.10	$ 0.10	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.38	$ 0.32	$ 0.32