Stockholders' Equity (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2015	Sep. 14, 2017	Sep. 30, 2016	Aug. 04, 2014
Class of Stock [Line Items]
Preferred stock, shares authorized	5,000,000			5,000,000
Common stock, shares authorized	500,000,000			500,000,000
Stock authorized to repurchase			$ 500,000,000		$ 600,000,000
Repurchases of common stock, value	$ 50,991,000	$ 64,940,000
Series A Junior Participating Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized	500,000
Common Stock [Member]
Class of Stock [Line Items]
Repurchases of common stock, shares	946,000	2,728,000
Repurchases of common stock, value	$ 10,000	$ 27,000