Stock-Based Compensation - Restricted Stock Units Granted - Tabular Disclosure (Details) - shares	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stocks granted (in shares)	789,409	507,556
Restricted Stock, Time Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stocks granted (in shares)	327,500	192,291
Board of Director Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stocks granted (in shares)	38,520	34,926
Restricted Stock, Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stocks granted (in shares)	423,389	280,339