Stock-based Compensation - Restricted Stock Awards (Details)	6 Months Ended
	Mar. 31, 2021 shares
Restricted Stock
Shares
Beginning of period (in shares)	1,406,154
Granted (in shares)	410,846
Vested (in shares)	(500,576)
Forfeited (in shares)	(15,490)
End of period (in shares)	1,300,934
Performance-Based Restricted Shares
Shares
Beginning of period (in shares)	796,024
Granted (in shares)	164,296
Vested (in shares)	(222,165)
Forfeited (in shares)	0
End of period (in shares)	738,155
Time-Based Restricted Shares
Shares
Beginning of period (in shares)	610,130
Granted (in shares)	246,550
Vested (in shares)	(278,411)
Forfeited (in shares)	(15,490)
End of period (in shares)	562,779