Earnings Per Share - Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Stock options
Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	529	179	529	550
Time-based restricted stock
Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	645	142	645	842
Performance-based restricted stock
Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	796	0	796	646