Stock-Based Compensation - Schedule of Weighted-Average Assumptions to Estimate Grant Date Fair Values (Details) - Shareholder Return [Member] - Performance Shares [Member]	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Assumptions:
Expected term (in years)	2 years 10 months 13 days	2 years 10 months 9 days	2 years 10 months 9 days
Expected volatility (as a percent)	31.16%	32.72%	32.27%
Risk-free interest rate (as a percent)	1.59%	2.80%	1.84%