Net Loss Per Common Share Net Loss per Common Share - Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator for basic and diluted net loss per share:
Net loss for basic	$ (19.2)	$ (12.9)
Denominator for basic and diluted net loss per share:
Weighted average common shares outstanding for basic	82.1	77.8
Dilutive potential common stock outstanding:
Basic and diluted net loss per share	$ (0.23)	$ (0.17)