Stock and Other Compensation Plans - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation cost	$ 23,900,000	$ 23,100,000	$ 24,600,000
Capitalized stock-based compensation cost	11,100,000	9,000,000	9,800,000
Stock-based compensation cost tax benefit	$ 2,300,000	4,400,000	5,000,000
Maximum shares authorized (in shares)	11,200,000.0
Shares were available for future issuance (in shares)	1,800,000
Service period	3 years
Unrecognized compensation cost	$ 11,500,000
Cost recognition period	1 year 7 months
Fair value of restricted stock vested	$ 17,200,000	$ 23,400,000	$ 20,600,000
Minimum initial investment	1,250
Minimum cash payments	25
Maximum annual cash payments	$ 100,000