Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Shares outstanding, beginning (in shares) at Dec. 31, 2020		39,500,000
Shareholders' equity, beginning at Dec. 31, 2020	$ 367.1	$ 18.2	$ 349.8	$ (0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36.1		36.1
Issuance of common stock (in shares)		100,000
Issuance of common stock	0.0
Repurchase of common stock (in shares)		(1,000,000.0)
Repurchase of common stock	(193.9)	$ (22.0)	(171.9)
Taxes paid related to net share settlement of stock awards (in shares)		(100,000)
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		38,500,000
Shareholders' equity, ending at Mar. 31, 2021	202.2	$ 1.7	201.4	(0.9)
Shares outstanding, beginning (in shares) at Dec. 31, 2020		39,500,000
Shareholders' equity, beginning at Dec. 31, 2020	367.1	$ 18.2	349.8	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 205.8
Repurchase of common stock (in shares)	(248,310)
Shares outstanding, ending (in shares) at Sep. 30, 2021		38,300,000
Shareholders' equity, ending at Sep. 30, 2021	$ 338.8	$ 0.0	339.7	(0.9)
Shares outstanding, beginning (in shares) at Mar. 31, 2021		38,500,000
Shareholders' equity, beginning at Mar. 31, 2021	202.2	$ 1.7	201.4	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	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		38,500,000
Shareholders' equity, ending at Jun. 30, 2021	317.4	$ 8.8	309.5	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	61.4		61.4
Issuance of common stock	$ 2.5
Issuance of common stock, value		$ 2.5
Repurchase of common stock (in shares)	(248,310)	(200,000)
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		38,300,000
Shareholders' equity, ending at Sep. 30, 2021	338.8	$ 0.0	339.7	(0.9)
Shares outstanding, beginning (in shares) at Dec. 31, 2021		38,100,000
Shareholders' equity, beginning at Dec. 31, 2021	306.8	$ 0.0	307.7	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	42.1		42.1
Issuance of common stock (in shares)		100,000
Issuance of common stock	0.0
Repurchase of common stock (in shares)		(100,000)
Repurchase of common stock	(25.0)	$ (7.0)	(18.0)
Taxes paid related to net share settlement of stock awards (in shares)		(100,000)
Taxes paid related to net share settlement of stock awards	(13.1)		(13.1)
Stock-based compensation	7.0	$ 7.0
Shares outstanding, ending (in shares) at Mar. 31, 2022		38,000,000.0
Shareholders' equity, ending at Mar. 31, 2022	317.8	$ 0.0	318.7	(0.9)
Shares outstanding, beginning (in shares) at Dec. 31, 2021		38,100,000
Shareholders' equity, beginning at Dec. 31, 2021	306.8	$ 0.0	307.7	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 438.4
Repurchase of common stock (in shares)	(727,198)
Shares outstanding, ending (in shares) at Sep. 30, 2022		37,400,000
Shareholders' equity, ending at Sep. 30, 2022	$ 612.7	$ 0.0	613.6	(0.9)
Shares outstanding, beginning (in shares) at Mar. 31, 2022		38,000,000.0
Shareholders' equity, beginning at Mar. 31, 2022	317.8	$ 0.0	318.7	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	339.3		339.3
Repurchase of common stock (in shares)		(300,000)
Repurchase of common stock	(61.5)	$ (7.4)	(54.1)
Taxes paid related to net share settlement of stock awards	(0.1)		(0.1)
Stock-based compensation	7.4	$ 7.4
Shares outstanding, ending (in shares) at Jun. 30, 2022		37,700,000
Shareholders' equity, ending at Jun. 30, 2022	602.9	$ 0.0	603.8	(0.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57.0		57.0
Issuance of common stock	$ 2.7
Issuance of common stock, value		$ 2.7
Repurchase of common stock (in shares)	(288,781)	(300,000)
Repurchase of common stock	$ (59.0)	$ (11.8)	(47.2)
Stock-based compensation	9.1	$ 9.1
Shares outstanding, ending (in shares) at Sep. 30, 2022		37,400,000
Shareholders' equity, ending at Sep. 30, 2022	$ 612.7	$ 0.0	$ 613.6	$ (0.9)