Income Per Share of Common Stock - Reconciliation of Numerator and Denominator (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net income	$ 5.9	$ 5.1
Income allocated to participating securities	(0.1)	(0.1)
Net income for basic and diluted earnings per share	$ 5.8	$ 5.0
Denominator:
Basic weighted average shares (in shares)	72.3	63.0
Employee stock options and stock purchase plan (in shares)	0.0	0.1
Diluted weighted average shares (in shares)	72.3	63.1
Basic and Diluted
Net income per share (in USD per share)	$ 0.08	$ 0.08