Earnings Per Share (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
Earnings Per Share Reconciliation:
Net earnings	$ 52,621	$ 67,919	$ 60,159	$ 42,243	$ 56,180	$ 62,463	$ 61,535	$ 54,909	$ 222,942	$ 235,087	$ 245,993
Total weighted average basic shares									147,179,000	156,353,000	159,933,000
Dilutive securities:
Stock options and stock award programs (in shares)									1,624,000	1,873,000	3,486,000
Total weighted average diluted shares									148,803,000	158,226,000	163,419,000
Earnings per share:
Basic (in dollars per share)	$ 0.36	$ 0.47	$ 0.41	$ 0.28	$ 0.36	$ 0.40	$ 0.39	$ 0.35	$ 1.51	$ 1.50	$ 1.54
Diluted (in dollars per share)	$ 0.36	$ 0.46	$ 0.41	$ 0.28	$ 0.36	$ 0.39	$ 0.39	$ 0.35	$ 1.50	$ 1.49	$ 1.51
Common stock potentially outstanding but not included in the computation of diluted earnings per share
Options to purchase shares not included in the computation of diluted earnings per share since the options were anti-dilutive (in shares)									1,061,068	1,090,459	130,952