Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 7,536	$ 33,474	$ 112,340	$ 77,348	$ (286)	$ 28,014	$ 102,084	$ 62,384	$ 230,698	$ 192,196	$ 189,588
Less: Income from continuing operations allocated to participating securities									775	793	1,980
Income from continuing operations available to common shareholders									229,923	191,403	187,608
Basic weighted average shares outstanding (shares)									90,533,000	90,150,000	90,201,000
Income per share from continuing operations - basic (usd per share)	$ 0.08	$ 0.37	$ 1.24	$ 0.85	$ 0.00	$ 0.31	$ 1.12	$ 0.68	$ 2.54	$ 2.12	$ 2.08
Basic Earnings per Share from Discontinued Operations
Income from discontinued operations									12,496	24,521	18,013
Less: Income from discontinued operations allocated to participating securities									42	101	188
Income from discontinued operations available to common shareholders									12,454	24,420	17,825
Income (loss) from discontinued operations per share - Basic (usd per share)	$ 0.00	$ 0.06	$ 0.04	$ 0.04	$ 0.09	$ 0.03	$ 0.08	$ 0.07	$ 0.14	$ 0.27	$ 0.20
Net income per share — basic (usd per share)	$ 0.08	$ 0.43	$ 1.28	$ 0.89	$ 0.09	$ 0.34	$ 1.20	$ 0.75	$ 2.68	$ 2.39	$ 2.28
Diluted Earnings per Share from Continuing Operations
Effect of dilutive stock options and other shares									5	4	4
Income (loss) from continuing operations available to common shareholders									229,928	191,407	187,612
Additional dilutive stock options and other shares									1,178,000	1,022,000	451,000
Diluted weighted average shares outstanding (shares)									91,711,000	91,172,000	90,652,000
Income per share from continuing operations - diluted (usd per share)	$ 0.08	$ 0.36	$ 1.23	$ 0.85	$ 0.00	$ 0.31	$ 1.12	$ 0.68	$ 2.50	$ 2.10	$ 2.07
Diluted Earnings per Share from Discontinued Operations
Effect of dilutive stock options and other shares									0	0	0
Income from discontinued operations available to common shareholders									$ 12,454	$ 24,420	$ 17,825
Additional dilutive stock options and other shares									1,178,000	1,022,000	451,000
Diluted weighted average shares outstanding									91,711,000	91,172,000	90,652,000
Income per share from discontinued operations - diluted (usd per share)	$ 0.00	$ 0.06	$ 0.04	$ 0.03	$ 0.09	$ 0.03	$ 0.08	$ 0.07	$ 0.14	$ 0.27	$ 0.20
Net income per share — diluted (usd per share)	$ 0.08	$ 0.42	$ 1.27	$ 0.88	$ 0.09	$ 0.34	$ 1.20	$ 0.75	$ 2.64	$ 2.37	$ 2.27
Earnings Per Share Diluted Other Disclosures Abstract
Anti-dilutive stock options excluded from computation of diluted earnings per share									0	0	0