Net Loss Per Share and Shareholders' Equity - Reconciliation of Numerator and Denominator of the Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net loss applicable to common shareholders	$ (27.2)	$ (2.1)	$ (43.1)	$ (10.3)
Denominator:
Denominator for basic EPS–weighted-average common shares (in shares)	53,237,740	52,164,034	52,765,856	52,133,076
Dilutive effect of stock-based compensation arrangements (in shares)	0	0	0	0
Denominator for diluted EPS–adjusted weighted-average common shares (in shares)	53,237,740	52,164,034	52,765,856	52,133,076
Basic EPS (in dollars per share)	$ (0.51)	$ (0.04)	$ (0.82)	$ (0.20)
Diluted EPS (in dollars per share)	$ (0.51)	$ (0.04)	$ (0.82)	$ (0.20)