Accumulated Stockholders' Equity (Deficit) (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended						7 Months Ended	18 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2014 Share Repurchase Program	Sep. 30, 2013 Share Repurchase Program	Sep. 30, 2012 Share Repurchase Program fund	Sep. 30, 2013 2013 Share Repurchase Program	Aug. 19, 2014 2013 Share Repurchase Program	Mar. 31, 2013 2013 Share Repurchase Program	Aug. 20, 2014 2014 Share Repurchase Program
Accumulated Stockholders' Equity (Deficit)
Common stock, shares authorized (in shares)	500,000	500,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000	50,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	155,104	164,762
Common stock, shares outstanding	154,668	164,425
Preferred stock issued (in shares)	0	0
Share repurchase program
Amount of shares authorized to be repurchased									$ 700,000,000	$ 1,000,000,000
Common stock shares repurchased and retired (in shares)				12,600	18,900	7,600	8,500	21,100
Cost of repurchase and retirement of common stock	$ 333,291,000	$ 509,704,000	$ 200,000,000	$ 333,300,000	$ 509,700,000	$ 200,000,000		$ 576,600,000
Number of venture capital investment funds from which common stock repurchased and retired						2