Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss	Noncontrolling Interest
Shares outstanding, beginning (in shares) at Dec. 31, 2017			46,200
Shareholders' equity, beginning at Dec. 31, 2017	$ 640.3		$ 7.3	$ 634.3		$ (1.3)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	352.8			352.8
Issuance of common stock (in shares)			300
Issuance of common stock	1.5		$ 1.5
Repurchase of common stock (in shares)			(6,100)
Repurchase of common stock	(533.9)		$ (29.9)	(504.0)
Taxes paid related to net share settlement of stock awards (in shares)			(100)
Taxes paid related to net share settlement of stock awards	(15.6)			(15.6)
Issuance of restricted stock awards, net of forfeitures (in shares)			100
Stock-based compensation	$ 21.1		$ 21.1
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Cash dividends	$ (23.0)			(23.0)
Foreign currency translation, net of tax	0.6					0.6
Change in pension benefits, net of tax	(0.2)					(0.2)
Shares outstanding, ending (in shares) at Dec. 31, 2018			40,400
Shareholders' equity, ending at Dec. 31, 2018	473.3	$ 29.7	$ 0.0	474.2	$ 29.7	(0.9)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	137.2			137.5			(0.3)
Contributions from noncontrolling interest	3.0						3.0
Issuance of common stock (in shares)			200
Issuance of common stock	1.9		$ 1.9
Repurchase of common stock (in shares)			(900)
Repurchase of common stock	(93.0)		$ (25.7)	(67.3)
Taxes paid related to net share settlement of stock awards (in shares)			(100)
Taxes paid related to net share settlement of stock awards	(11.5)			(11.5)
Issuance of restricted stock awards, net of forfeitures (in shares)			100
Stock-based compensation	$ 23.8		$ 23.8
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Cash dividends	$ (23.4)			(23.4)
Foreign currency translation, net of tax	0.0
Change in pension benefits, net of tax	0.0
Shares outstanding, ending (in shares) at Dec. 31, 2019			39,700
Shareholders' equity, ending at Dec. 31, 2019	511.0	(0.3)	$ 0.0	509.2	(0.3)	(0.9)	2.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(82.1)			(81.9)			(0.2)
Purchase of noncontrolling interest	(3.0)			(0.5)			(2.5)
Issuance of common stock (in shares)			100
Issuance of common stock	2.4		$ 2.4
Repurchase of common stock (in shares)			(200)
Repurchase of common stock	(27.9)		$ (4.3)	(23.6)
Taxes paid related to net share settlement of stock awards (in shares)			(100)
Taxes paid related to net share settlement of stock awards	(18.7)		$ (3.6)	(15.1)
Stock-based compensation	23.7		$ 23.7
Cash dividends	(25.1)			(25.1)
Foreign currency translation, net of tax	0.0
Change in pension benefits, net of tax	0.0
Shares outstanding, ending (in shares) at Dec. 31, 2020			39,500
Shareholders' equity, ending at Dec. 31, 2020	367.1	$ (0.5)	$ 18.2	349.8	$ (0.5)	$ (0.9)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash settlement of stock awards	$ (12.7)			$ (12.7)