Accumulated Stockholders' Deficit - Share Repurchase Program (Details) - USD ($) shares in Millions	1 Months Ended	9 Months Ended
	Aug. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
2017 Share Repurchase program
Share Repurchase Program
Amount of shares authorized to be repurchased	$ 1,000,000,000
Term of share repurchase program	4 years
Common stock shares repurchased and retired (in shares)		9.9
Cost of repurchase and retirement of common stock		$ 164,600,000
2014 Share Repurchase Program
Share Repurchase Program
Common stock shares repurchased and retired (in shares)			13.1
Cost of repurchase and retirement of common stock			$ 286,500,000