Earnings Per Share, Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Net income	$ 26.3	$ (292.2)
Denominator — Weighted-average common shares outstanding (in thousands):
Basic	17,864	17,344
Add: dilutive effect of non-vested common shares, restricted stock units and performance shares	336	0
Diluted	18,200	17,344
Net income (loss) per common share:
Basic	$ 1.47	$ (16.85)
Earnings per common share, Diluted:
Diluted	$ 1.44	$ (16.85)