Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ 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, 2019			39.7
Shareholders' equity, beginning at Dec. 31, 2019	$ 511.0	$ (0.5)	$ 0.0	$ 509.2	$ (0.5)	$ (0.9)	$ 2.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(23.5)			(23.4)			(0.1)
Repurchase of common stock (in shares)			(0.3)
Repurchase of common stock	(27.9)		$ (4.3)	(23.6)
Cash settlement of stock awards	(12.7)			(12.7)
Taxes paid related to net share settlement of stock awards	(15.1)			(15.1)
Stock-based compensation	4.3		$ 4.3
Shares outstanding, ending (in shares) at Mar. 31, 2020			39.4
Shareholders' equity, ending at Mar. 31, 2020	435.6		$ 0.0	433.9		(0.9)	2.6
Shares outstanding, beginning (in shares) at Dec. 31, 2019			39.7
Shareholders' equity, beginning at Dec. 31, 2019	511.0	$ (0.5)	$ 0.0	509.2	$ (0.5)	(0.9)	2.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(99.2)
Shares outstanding, ending (in shares) at Sep. 30, 2020			39.5
Shareholders' equity, ending at Sep. 30, 2020	372.2		$ 15.5	357.6		(0.9)	0.0
Shares outstanding, beginning (in shares) at Mar. 31, 2020			39.4
Shareholders' equity, beginning at Mar. 31, 2020	435.6		$ 0.0	433.9		(0.9)	2.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(118.8)			(118.8)
Stock-based compensation	6.1		$ 6.1
Other	(0.2)			(0.2)
Shares outstanding, ending (in shares) at Jun. 30, 2020			39.4
Shareholders' equity, ending at Jun. 30, 2020	322.7		$ 6.1	314.9		(0.9)	2.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	43.1			43.2			(0.1)
Purchase of noncontrolling interest	(3.0)			(0.5)			(2.5)
Issuance of common stock (in shares)			0.1
Issuance of common stock	2.5		$ 2.5
Stock-based compensation	6.9		$ 6.9
Shares outstanding, ending (in shares) at Sep. 30, 2020			39.5
Shareholders' equity, ending at Sep. 30, 2020	372.2		$ 15.5	357.6		(0.9)	0.0
Shares outstanding, beginning (in shares) at Dec. 31, 2020			39.5
Shareholders' equity, beginning at Dec. 31, 2020	367.1		$ 18.2	349.8		(0.9)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	36.1			36.1
Issuance of common stock (in shares)			0.1
Issuance of common stock	0.0
Repurchase of common stock (in shares)			(1.0)
Repurchase of common stock	(193.9)		$ (22.0)	(171.9)
Taxes paid related to net share settlement of stock awards (in shares)			(0.1)
Taxes paid related to net share settlement of stock awards	(12.6)			(12.6)
Stock-based compensation	5.5		$ 5.5
Shares outstanding, ending (in shares) at Mar. 31, 2021			38.5
Shareholders' equity, ending at Mar. 31, 2021	202.2		$ 1.7	201.4		(0.9)	0.0
Shares outstanding, beginning (in shares) at Dec. 31, 2020			39.5
Shareholders' equity, beginning at Dec. 31, 2020	367.1		$ 18.2	349.8		(0.9)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	205.8
Shares outstanding, ending (in shares) at Sep. 30, 2021			38.3
Shareholders' equity, ending at Sep. 30, 2021	338.8		$ 0.0	339.7		(0.9)	0.0
Shares outstanding, beginning (in shares) at Mar. 31, 2021			38.5
Shareholders' equity, beginning at Mar. 31, 2021	202.2		$ 1.7	201.4		(0.9)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	108.3			108.3
Stock-based compensation	7.1		$ 7.1
Other	(0.2)			(0.2)
Shares outstanding, ending (in shares) at Jun. 30, 2021			38.5
Shareholders' equity, ending at Jun. 30, 2021	317.4		$ 8.8	309.5		(0.9)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	61.4			61.4
Issuance of common stock	2.5		$ 2.5
Repurchase of common stock (in shares)			(0.2)
Repurchase of common stock	(50.0)		$ (19.1)	(30.9)
Taxes paid related to net share settlement of stock awards	(0.3)			(0.3)
Stock-based compensation	7.8		$ 7.8
Shares outstanding, ending (in shares) at Sep. 30, 2021			38.3
Shareholders' equity, ending at Sep. 30, 2021	$ 338.8		$ 0.0	$ 339.7		$ (0.9)	$ 0.0