CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Treasury Stock, At Cost	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Europe	Europe Accumulated Other Comprehensive Income (Loss)	France	France Accumulated Other Comprehensive Income (Loss)
Balances (in shares) at Dec. 31, 2016		36,924,000
Balances at Dec. 31, 2016	$ 214.4	$ 0.4	$ 185.5	$ (23.9)	$ 73.1	$ (20.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	1.6		1.6
Issuance of restricted stock (in shares)		68,000
Issuance of restricted stock	0.0		(0.8)	0.8
Stock withheld for employee taxes (in shares)		(48,000)
Stock withheld for employee taxes	(0.8)		(0.3)	(0.5)
Cancellation of restricted shares (in shares)		(8,000)
Cancellation of restricted shares	(0.1)		0.0	(0.1)
Proceeds from issuance of common stock (in shares)		158,000
Proceeds from issuance of common stock	2.4		0.5	1.9
Dividends	(68.7)				(68.7)
Discontinued European entities cumulative translation adjustment							$ 14.4	$ 14.4
Change in cumulative translation adjustment	8.2					8.2
Net income	40.4				40.4
Balances (in shares) at Dec. 31, 2017		37,094,000
Balances at Dec. 31, 2017	211.8	$ 0.4	186.5	(21.8)	44.8	1.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	2.8		2.8
Issuance of restricted stock (in shares)		117,000
Issuance of restricted stock	0.0		(1.7)	1.7
Stock withheld for employee taxes (in shares)		(62,000)
Stock withheld for employee taxes	(1.9)		0.0	(1.9)
Proceeds from issuance of common stock (in shares)		419,000
Proceeds from issuance of common stock	5.4		(0.6)	6.0
Dividends	$ (297.1)				(297.1)
Repurchase of treasury shares (in shares)	(232,550)	(233,000)
Repurchase of treasury shares	$ (9.1)			(9.1)
Discontinued European entities cumulative translation adjustment									$ 4.1	$ 4.1
Change in cumulative translation adjustment	(3.0)					(3.0)
Net income	224.7				224.7
Balances (in shares) at Dec. 31, 2018		37,335,000
Balances at Dec. 31, 2018	137.7	$ 0.4	187.0	(25.1)	(27.6)	3.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5.4		5.4
Issuance of restricted stock (in shares)		109,000
Issuance of restricted stock	0.0		(1.8)	1.8
Stock withheld for employee taxes (in shares)		(39,000)
Stock withheld for employee taxes	(0.9)			(0.9)
Proceeds from issuance of common stock (in shares)		230,000
Proceeds from issuance of common stock	2.1		(1.7)	3.8
Dividends	(18.1)				(18.1)
Issuance of shares under employee stock purchase plan (shares)		44,000
Issuance of shares under employee stock purchase plan	0.8		0.8
Change in cumulative translation adjustment	0.0					0.0
Net income	48.5				48.5
Balances (in shares) at Dec. 31, 2019		37,679,000
Balances at Dec. 31, 2019	$ 175.5	$ 0.4	$ 189.7	$ (20.4)	$ 2.8	$ 3.0