Equity Incentive Plans - Restricted Stock Units Granted (Details) - shares		12 Months Ended
	Nov. 08, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	468,700	1,018,570	1,690,582	1,513,281
Restricted Stock, Time Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		386,713	744,250	597,250
Board of Director Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		43,519	86,082	69,281
Restricted Stock, Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		588,338	860,250	846,750