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		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net earnings	$ 68,313	$ 91,318	$ 109,883	$ 144,691
Denominator:
Basic	63,278	62,266	63,043	62,128
Dilutive effect of stock options and restricted stock	2,376	2,298	2,231	2,494
Diluted shares outstanding	65,654	64,564	65,274	64,622
Income per common share:
Basic earnings per share	$ 1.08	$ 1.47	$ 1.74	$ 2.33
Diluted earnings per share	$ 1.04	$ 1.41	$ 1.68	$ 2.24