Earnings Per Common Share (Computation of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net Income
Basic earnings per share	$ 89,981	$ 51,711	$ 248,331	$ 176,645
Stock options	0	0	0	0
Restricted stock	0	0	0	0
Diluted earnings per share	$ 89,981	$ 51,711	$ 248,331	$ 176,645
Shares
Basic earnings per share (in shares)	65,062	65,362	65,441	65,221
Stock options (in shares)	304	191	367	281
Restricted stock (in shares)	492	270	372	213
Diluted earnings per share (in shares)	65,858	65,823	66,180	65,715
Per Share Amount
Basic earnings per share (in dollars per share)	$ 1.38	$ 0.79	$ 3.79	$ 2.71
Stock options (in dollars per share)	$ 0.00	$ 0.00	$ (0.02)	$ (0.01)
Restricted stock (in dollars per share)	$ (0.01)	$ 0.00	$ (0.02)	$ (0.01)
Diluted earnings per share (in dollars per share)	$ 1.37	$ 0.79	$ 3.75	$ 2.69
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options, excluded in the calculation of earnings per share	283	672	283	672