Stock and Other Compensation Plans - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Payment Arrangement [Abstract]
Stock-based compensation cost	$ 23,900,000	$ 23,900,000	$ 23,100,000
Capitalized stock-based compensation cost	12,800,000	11,100,000	9,000,000.0
Stock-based compensation cost tax benefit	$ 700,000	2,300,000	4,400,000
Maximum shares authorized (in shares)	11,200,000
Shares available for future issuance	1,500,000
Service period	3 years
Unrecognized compensation cost	$ 13,700,000
Cost recognition period	1 year 7 months 6 days
Fair value of restricted stock vested	$ 20,500,000	$ 17,200,000	$ 23,400,000
Minimum initial investment	1,250
Minimum cash payments	25
Maximum annual cash payments	$ 100,000