Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share Basic Two Class Method [Abstract]
Income from Continuing Operations, Net of Tax	$ 35,853	$ 70,808	$ 162,012	$ 114,038	$ 34,850	$ 66,143	$ 143,003	$ 101,546	$ 382,711	$ 345,542	$ 305,623
Less: Income allocated to participating securities									475	538	607
Income from continuing operations available to common shareholders									$ 382,236	$ 345,004	$ 305,016
Weighted Average Number of Shares Outstanding, Basic and Diluted									106,100	103,524	101,892
Income (Loss) from Continuing Operations, Per Basic and Diluted Share	$ 0.34	$ 0.67	$ 1.52	$ 1.08	$ 0.33	$ 0.64	$ 1.39	$ 0.99	$ 3.60	$ 3.33	$ 3.00
Net income from discontinued operations, net of tax									$ 13,710	$ 4,562	$ 9,452
Undistributed Discontinued Operation Earnings (Loss), Allocation to Participating Securities, Basic									12	8	19
Net Income (Loss) from Discontinued Operations Available to Common Shareholders, Basic									$ 13,698	$ 4,554	$ 9,433
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic and Diluted Share									$ 0.13	$ 0.05	$ 0.09
Earnings Per Share, Basic and Diluted	$ 0.34	$ 0.67	$ 1.55	$ 1.19	$ 0.33	$ 0.69	$ 1.38	$ 1.00	$ 3.73	$ 3.38	$ 3.09