Supplemental Quarterly Financial Data (Unaudited) (Quarterly Financial Information) (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
Quarterly Financial Data
Net sales	$ 590,922	$ 507,664	$ 479,382	$ 445,110	$ 562,625	$ 494,810	$ 493,222	$ 487,646	$ 2,023,078	$ 2,038,303	$ 2,001,240
Gross margin	165,620	136,942	133,243	111,733	159,690	143,389	137,620	143,886
Earnings before income taxes	80,756	63,408	54,366	27,956	68,727	57,559	57,591	57,072	226,486	240,949	227,244
Net Earnings:
Net earnings	$ 63,147	$ 51,047	$ 40,824	$ 25,820	$ 50,060	$ 43,753	$ 43,855	$ 43,784	$ 180,838	$ 181,452	$ 165,844
Earnings per share:
Basic earnings per share	$ 1.03	$ 0.83	$ 0.66	$ 0.41	$ 0.79	$ 0.68	$ 0.67	$ 0.67	$ 2.92	$ 2.81	$ 2.50
Diluted earnings per share	0.99	0.81	0.65	0.40	0.77	0.66	0.66	0.66	2.85	2.75	2.45
Cash dividends per share	$ 0.11	$ 0.11	$ 0.11	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.08	$ 0.43	$ 0.38	$ 0.32