Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Numerator:
Income from continuing operations	$ 129,763	$ 98,961	$ 274,060	$ 203,326
Loss from discontinued operations	(44)	(171)	(55)	(386)
NET INCOME	129,719	98,790	274,005	202,940
Adjustment for basic earnings per share:
Earnings allocated to unvested shareholders	(530)	(300)	(1,009)	(599)
Numerator for basic earnings per share:
From continuing operations	129,233	98,661	273,051	202,727
From discontinued operations	(44)	(171)	(55)	(386)
Net income (loss) attributable to parent, basic	129,189	98,490	272,996	202,341
Adjustment for diluted earnings per share:
Effect of reallocating undistributed earnings of unvested shareholders	7	6	14	11
Numerator for diluted earnings per share:
From continuing operations	129,240	98,667	273,065	202,738
From discontinued operations	(44)	(171)	(55)	(386)
Net income (loss) attributable to parent, diluted	$ 129,196	$ 98,496	$ 273,010	$ 202,352
Denominator:
Denominator for basic earnings per share - weighted-average shares (in shares)	107,385	106,515	107,285	106,270
Effect of dilutive shares from stock options and restricted stock (in shares)	1,657	2,080	1,640	2,105
Denominator for diluted earnings per share - adjusted weighted-average shares (in shares)	109,042	108,595	108,925	108,375
Basic earnings per common share:
Income from continuing operations (in dollars per share)	$ 1.20	$ 0.92	$ 2.54	$ 1.90
Net income (in dollars per share)	$ 1.20	$ 0.92	$ 2.54	$ 1.90
Diluted earnings per common share:
Income from continuing operations (in dollars per share)	$ 1.18	$ 0.91	$ 2.51	$ 1.87
Net income (in dollars per share)	$ 1.18	$ 0.91	$ 2.51	$ 1.87
Outstanding equity awards
Shares excluded from calculation of diluted earnings per share (in shares)	435	313	453	324
Weighted-average price per share (in dollars per share)	$ 59.76	$ 47.94	$ 59.76	$ 47.94