Stock-Based Compensation - Schedule of Option Compensation Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted average grant date fair value per option granted	$ 7.86	$ 5.97	$ 10.40
Fair value of options vested	$ 3.0	$ 2.8	$ 6.8
Intrinsic value of options exercised	7.5	8.5	0.1
Excess tax benefit for tax deductions related to the exercise of stock options	1.2	0.0	0.0
Cash received from option exercises, net of tax withholding	1.9	12.9	0.0
Tax benefits for stock-option compensation expense	$ 0.7	$ 0.5	$ 0.2