Earnings Per Share, Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 26.0	$ 20.2	$ 52.3	$ (272.0)
Denominator — Weighted-average common shares outstanding (in thousands):
Basic (shares)	17,871	17,006	17,867	17,233
Add: dilutive effect of non-vested common shares, restricted stock units, performance shares and stock options (shares)	323	247	327	0
Add: dilutive effect of warrants (shares)	0	939	0	0
Diluted (shares)	18,194	18,192	18,194	17,233
Net income (loss) per common share:
Basic (in dollars per share)	$ 1.45	$ 1.19	$ 2.92	$ (15.78)
Earnings per common share, Diluted:
Diluted (in dollars per share)	$ 1.43	$ 1.11	$ 2.87	$ (15.78)