Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Former Parent's Net Investment	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning balance at Dec. 31, 2016	$ 1,341.8	$ 1,360.2	$ 0.0	$ 0.0	$ 0.0	$ (18.4)	$ 0.0
Beginning balance, shares at Dec. 31, 2016			0				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	89.7	89.7
Other comprehensive loss	(1.4)					(1.4)
Capital contribution from Former Parent	0.0
Net transfers from Former Parent and affiliates	(31.2)	(31.2)
Restricted shares, net	9.0	9.0
Ending balance at Dec. 31, 2017	1,407.9	1,427.7	$ 0.0	0.0	0.0	(19.8)	$ 0.0
Ending balance, shares at Dec. 31, 2017			0				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adopting new accounting standards (see Note 1)	(4.0)	(4.0)
Net income	75.7	53.8			21.9
Cash dividends on common stock	(2.4)				(2.4)
Other comprehensive loss	2.1					2.1
Capital contribution from Former Parent	200.0	200.0
Net transfers from Former Parent and affiliates	(1.2)	(1.2)
Restricted shares, net		(1,684.6)	$ 0.5	1,684.1
Distribution by Former Parent, shares			48,800,000
Restricted shares, net	9.4	8.3		1.6			$ (0.5)
Restricted shares, net, shares							0
Other	(3.0)						$ (3.0)
Shares repurchased, shares							(100,000)
Ending balance at Dec. 31, 2018	1,684.5	0.0	$ 0.5	1,685.7	19.5	(17.7)	$ (3.5)
Ending balance, shares at Dec. 31, 2018			48,800,000				(100,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	113.3				113.3
Cash dividends on common stock	(9.9)				(9.9)
Other comprehensive loss	(2.0)					(2.0)
Capital contribution from Former Parent	0.0
Restricted shares, net	10.3			16.0			$ (5.7)
Restricted shares, net, shares			200,000				(200,000)
Other	(11.0)						$ (11.0)
Treasury Stock, Shares, Retired			(700,000)				700,000
Treasury Stock, Retired, Cost Method, Amount				(20.2)			$ 20.2
Stockholders' Equity, Other	$ 5.2			5.2
Shares repurchased, shares	361,442						(400,000)
Ending balance at Dec. 31, 2019	$ 1,790.4	$ 0.0	$ 0.5	$ 1,686.7	$ 122.9	$ (19.7)	$ 0.0
Ending balance, shares at Dec. 31, 2019			48,300,000				0