Earnings Per Share, Calculation of EPS (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Numerator:
Net income	$ 24.5		$ 18.6		$ 40.3		$ 52.1
Denominator — Weighted-average common shares outstanding (in thousands):
Basic	17,841	[1]	18,742	[1]	17,889	[1]	19,027	[1]
Add: dilutive effect of non-vested common shares, restricted stock units and performance shares	112		112		133		135
Add: dilutive effect of warrants	505		91		490		94
Diluted	18,458	[2]	18,945	[2]	18,512	[2]	19,256	[2]
Earnings per common share, Basic:
Net income per share	$ 1.38		$ 0.99		$ 2.25		$ 2.73
Earnings per common share, Diluted:
Net income per share	$ 1.33		$ 0.98		$ 2.18		$ 2.70

[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.