Accumulated Stockholders' Deficit - Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Share repurchase program
Cost of repurchase and retirement of common stock		$ 207,312	$ 227,559	$ 333,291
Preferred stock
Preferred Stock, Shares Authorized		50,000	50,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01	$ 0.01
Preferred Stock, Shares Issued		0	0
2014 Share Repurchase Program
Share repurchase program
Amount of shares authorized to be repurchased	$ 1,000,000
Term of share repurchase program	3 years
Common stock shares repurchased and retired (in shares)		7,800	8,100
Cost of repurchase and retirement of common stock		$ 207,300	$ 227,600
2013 Share Repurchase Program
Share repurchase program
Common stock shares repurchased and retired (in shares)				12,600
Cost of repurchase and retirement of common stock				$ 333,300