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, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net earnings	$ 91,318	$ 77,579	$ 144,691	$ 126,699
Denominator:
Basic shares outstanding	62,266	62,175	62,128	61,995
Dilutive effect of stock options and restricted stock	2,298	2,389	2,494	2,312
Diluted shares outstanding	64,564	64,564	64,622	64,307
Income per common share:
Basic earnings per share	$ 1.47	$ 1.25	$ 2.33	$ 2.04
Diluted earnings per share	$ 1.41	$ 1.20	$ 2.24	$ 1.97