Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	APIC	Retained Earnings	AOCI
Balance (in shares) at Dec. 31, 2018		46,767,164
Beginning balance at Dec. 31, 2018	$ 807.3	$ 0.5	$ (940.3)	$ 539.0	$ 1,208.1	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5.3				5.3
Purchase of treasury stock	(13.3)		(13.3)
Issuance of treasury stock	0.0		5.6	(5.6)
Amounts related to share-based compensation	(4.1)			(4.1)
Share-based compensation expense	2.6			2.6
Balance (in shares) at Mar. 31, 2019		46,767,164
Ending balance at Mar. 31, 2019	797.8	$ 0.5	(948.0)	531.9	1,213.4	0.0
Balance (in shares) at Dec. 31, 2019		46,767,164
Beginning balance at Dec. 31, 2019	803.0	$ 0.5	(1,099.8)	538.7	1,362.9	0.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	89.3				89.3
Loss on interest rate hedge, net of tax	(2.7)					(2.7)
Purchase of treasury stock	(140.6)		(140.6)
Issuance of treasury stock	(0.5)		5.2	(5.7)
Amounts related to share-based compensation	(5.6)			(5.6)
Share-based compensation expense	2.8			2.8
Balance (in shares) at Mar. 31, 2020		46,767,164
Ending balance at Mar. 31, 2020	$ 746.8	$ 0.5	$ (1,235.2)	$ 530.2	$ 1,453.3	$ (2.0)