Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2016		37,228,144
Balance at Dec. 31, 2016	$ 127.8	$ 0.0	$ 197.3	$ (64.6)	$ (4.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for options issued	1.4		1.4
Share-based compensation for restricted stock issued (in shares)		1,864,265
Share-based compensation for restricted stock issued	20.6		20.6
Tax withholding related to the vesting of restricted stock units (in shares)		(257,613)
Tax withholding related to the vesting of restricted stock	(4.0)		(4.0)
Shares issued in connection with employee stock purchase plan (in shares)		28,958
Stock issued in connection with employee stock purchase plan	0.9		0.9
Stock issued in connection with acquisitions (in shares)		5,229,813
Stock issued in connection with acquisitions	$ 141.9		141.9
Stock options exercised (in shares)	438,338	438,338
Stock options exercised	$ 2.1		2.1
Net loss	(71.5)			(71.5)
Foreign currency translation	1.0				1.0
Balance (in shares) at Dec. 31, 2017		44,531,905
Balance at Dec. 31, 2017	231.4	$ 0.0	360.2	(124.9)	(3.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for options issued	1.1		1.1
Share-based compensation for restricted stock issued (in shares)		1,590,042
Share-based compensation for restricted stock issued	33.3		33.3
Tax withholding related to the vesting of restricted stock units (in shares)		(478,320)
Tax withholding related to the vesting of restricted stock	(21.0)		(21.0)
Shares issued in connection with employee stock purchase plan (in shares)		34,616
Stock issued in connection with employee stock purchase plan	1.3		1.3
Stock issued in connection with acquisitions (in shares)		195,124
Stock issued in connection with acquisitions	8.8		8.8
Equity offerings, net of issuance costs (in shares)		9,589,094
Equity offerings, net of issuance costs	$ 424.5		424.5
Stock options exercised (in shares)	162,688	162,688
Stock options exercised	$ 1.7		1.7
Net loss	(243.4)			(243.4)
Foreign currency translation	(23.0)				(23.0)
Balance (in shares) at Dec. 31, 2018		55,625,149
Balance at Dec. 31, 2018	414.7	$ 0.0	809.9	(368.3)	(26.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for options issued	0.4		0.4
Share-based compensation for restricted stock issued (in shares)		915,634
Share-based compensation for restricted stock issued	30.8		30.8
Tax withholding related to the vesting of restricted stock units (in shares)		(28,002)
Tax withholding related to the vesting of restricted stock	(0.4)		(0.4)
Shares issued in connection with employee stock purchase plan (in shares)		93,862
Stock issued in connection with employee stock purchase plan	1.1		1.1
Stock issued in connection with acquisitions (in shares)		6,954
Stock issued in connection with acquisitions	$ (0.3)		(0.3)
Stock options exercised (in shares)	86,770	86,770
Stock options exercised	$ 0.9		0.9
Net loss	(105.9)			(105.9)
Foreign currency translation	(50.2)				(50.2)
Balance (in shares) at Dec. 31, 2019		56,686,459
Balance at Dec. 31, 2019	$ 291.1	$ 0.0	$ 842.4	$ (474.2)	$ (77.1)