Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income
Balance (in shares) at Dec. 31, 2018			88,685,920	2,274
Balance at Dec. 31, 2018		$ 911.5	$ 0.9	$ 0.0	$ 1,501.7	$ (591.1)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss		(6.0)				(6.0)
Stock-based compensation (in shares)			18,735
Stock-based compensation		4.1			4.1
Stock option exercises (in shares)			90,807
Stock option exercises		1.9			1.9
Gain (loss) on fair value of interest rate caps		(2.0)					(2.0)
Balance (in shares) at Mar. 31, 2019			88,795,462	2,274
Balance at Mar. 31, 2019		909.5	$ 0.9	$ 0.0	1,507.7	(597.5)	(1.6)
Balance (in shares) at Dec. 31, 2019			89,836,069	132,930
Balance at Dec. 31, 2019		923.4	$ 0.9	$ (4.1)	1,527.7	(598.1)	(3.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss		(6.3)				(6.3)
Stock-based compensation		1.6			1.6
Stock option exercises and performance stock units vested (in shares)			441,632
Stock option exercises and performance stock units vested		6.4			6.4
Stock repurchases (in shares)	[1]			45,610
Stock repurchases	[1]	(1.5)		$ (1.5)
Gain (loss) on fair value of interest rate caps		0.4					0.4
Balance (in shares) at Mar. 31, 2020			90,277,701	178,540
Balance at Mar. 31, 2020		$ 924.0	$ 0.9	$ (5.6)	$ 1,535.7	$ (604.4)	$ (2.6)

[1] Stock repurchases represent shares withheld by the Company to pay employee taxes associated with restricted stock unit vesting and performance stock unit vesting.