Earnings Per Share (Reconciliation of Net Earnings to Net Earnings Per Share Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Earnings Per Share
Net earnings	$ 63,147	$ 51,047	$ 40,824	$ 25,820	$ 50,060	$ 43,753	$ 43,855	$ 43,784	$ 180,838	$ 181,452	$ 165,844
Basic shares outstanding									61,893	64,684	66,432
Dilutive effect of stock options and restricted stock									1,663	1,372	1,344
Diluted shares outstanding									63,556	66,056	67,776
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