Stock-Based Compensation - Restricted Stock Units Granted (Details) - shares	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	471,151	951,266
Restricted Stock, Time Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	190,266	362,113
Board of Director Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	546	815
Restricted Stock, Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	280,339	588,338