Earnings Per Share, Calculation of EPS (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Numerator:
Net income	$ 15.8		$ 33.5
Denominator — Weighted-average common shares outstanding (in thousands):
Basic	17,921	[1]	19,143	[1]
Add: dilutive effect of non-vested common shares, restricted stock units, performance shares and market-based shares	122		131
Add: dilutive effect of warrants	471		92
Diluted	18,514	[2]	19,366	[2]
Earnings per common share, Basic:
Net income per share	$ 0.88		$ 1.75
Earnings per common share, Diluted:
Net income per share	$ 0.85		$ 1.73

[1] The basic weighted-average number of common shares outstanding during the period excludes non-vested common shares, restricted stock units, performance shares and market-based shares.

[2] The diluted weighted-average number of common shares outstanding during the periods were calculated using the treasury method.