Earnings per Common Share - Schedule of calculations of basic and diluted earnings per common share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 8.9	$ 13.5
Less: earnings and dividends allocated to participating securities	0.0	0.0
Earnings available for common stockholders used in calculation of basic earnings per share	$ 8.9	$ 13.5
Weighted average number of common shares outstanding, basic (in shares)	49.7	53.5
Basic earnings per common share (in dollars per share)	$ 0.18	$ 0.25
Earnings available for common stockholders used in calculation of diluted earnings per share	$ 8.9	$ 13.5
Effect of shares issuable under share-based compensation plans (in shares)	0.2	0.2
Weighted average number of common shares outstanding, diluted (in shares)	49.9	53.7
Diluted earnings per common share (in dollars per share)	$ 0.18	$ 0.25