Equity Incentive Plans - Performance-Based Grants (Details) - Restricted Stock, Performance Based Shares	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards granted, percentage (as a percent)	100.00%	100.00%	100.00%
Performance-based awards granted, percentage, maximum threshold met (as a percent)	200.00%
Performance goal measurement period (in years)	3 years