Net (Loss) Income Per Share, Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net (loss) income	$ 13.3	$ 22.1	$ 20.2	$ (292.2)	$ 15.6	$ 15.9	$ 24.5	$ 15.8	$ (236.6)	$ 71.8	$ 104.8
Denominator – Weighted-average common shares outstanding (in thousands):
Basic (in shares)									17,201	17,818	18,827
Add: dilutive effect of non-vested common shares, restricted stock units and performance shares									0	179	178
Add: dilutive effect of warrants									0	596	241
Diluted (in shares)									17,201	18,593	19,246
Net (loss) income per common share, Basic (in dollars per share)	$ 0.76	$ 1.29	$ 1.19	$ (16.85)	$ 0.88	$ 0.90	$ 1.38	$ 0.88	$ (13.76)	$ 4.02	$ 5.56
Net (loss) income per common share, Diluted (in dollars per share	$ 0.73	$ 1.21	$ 1.11	$ (16.85)	$ 0.85	$ 0.85	$ 1.33	$ 0.85	$ (13.76)	$ 3.86	$ 5.44