Earnings per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic:
Net income (loss)	$ 10.2	$ (15.5)	$ 0.8	$ (17.1)
Weighted average number of common shares outstanding during the period (in shares)	76,743,853	34,072,056	76,745,396	21,241,897
Net income (loss) per common share - basic (USD per share)	$ 0.13	$ (0.45)	$ 0.01	$ (0.81)
Diluted:
Net income (loss)	$ 10.2	$ (15.5)	$ 0.8	$ (17.1)
Denominator for diluted earnings per share:
Weighted average number of common shares outstanding during the period (in shares)	76,743,853	34,072,056	76,745,396	21,241,897
Incremental common shares attributable to outstanding dilutive options and unvested restricted shares (in shares)	85,015	0	84,900	0
Denominator for diluted earnings per common share (in shares)	76,828,868	34,072,056	76,830,296	21,241,897
Net income (loss) per common share - diluted (USD per share)	$ 0.13	$ (0.45)	$ 0.01	$ (0.81)
Period acquiree is included in operating activities	22 days		22 days