Stock-Based Compensation - Time-Based Grants (Details) - Restricted Stock, Time Based Shares	6 Months Ended
	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage (as a percent)	33.33%
Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage (as a percent)	33.33%
Share-based Compensation Award, Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage (as a percent)	33.33%