Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net Income
Net income	$ 99,505	$ 112,992	$ 261,023	$ 281,879
Stock options	0	0	0	0
Restricted stock and performance units	0	0	0	0
Diluted earnings per share	$ 99,505	$ 112,992	$ 261,023	$ 281,879
Shares
Basic earnings per share (in shares)	64,795,000	64,649,000	64,750,000	64,557,000
Stock options (in shares)	0	61,000	0	74,000
Restricted stock (in shares)	52,000	420,000	102,000	432,000
Diluted earnings per share (in shares)	64,847,000	65,130,000	64,852,000	65,063,000
Per Share Amount
Basic earnings per share (in dollars per share)	$ 1.54	$ 1.75	$ 4.03	$ 4.37
Stock options (in dollars per share)	0.00	0.00	0.00	0.00
Restricted stock (in dollars per share)	(0.01)	(0.02)	(0.01)	(0.04)
Diluted earnings per share (in dollars per share)	$ 1.53	$ 1.73	$ 4.02	$ 4.33
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options, excluded in the calculation of earnings per share	2,377,436	873,000	2,070,774	867,000