Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2019	$ 1,922.3	$ 0.1	$ 1,696.7	$ 315.4	$ (89.9)
Beginning balance (in shares) at Dec. 31, 2019		64.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	1.4		1.4
Stock-based compensation and vesting of restricted stock, net of withholdings (in shares)		0.4
Net income/(loss)	(116.6)			(116.6)
Dividends declared	(11.1)			(11.1)
Total comprehensive income/(loss), net of tax	(38.9)				(38.9)
Ending balance at Mar. 31, 2020	1,757.1	$ 0.1	1,698.1	187.7	(128.8)
Ending balance (in shares) at Mar. 31, 2020		64.6
Beginning balance at Dec. 31, 2020	1,996.7	$ 0.1	1,706.0	269.5	21.1
Beginning balance (in shares) at Dec. 31, 2020		64.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock, net of withholdings	0.4		0.4
Stock-based compensation and vesting of restricted stock, net of withholdings (in shares)		0.1
Net income/(loss)	39.2			39.2
Dividends declared	(3.9)			(3.9)
Total comprehensive income/(loss), net of tax	(40.6)				(40.6)
Ending balance at Mar. 31, 2021	$ 1,991.8	$ 0.1	$ 1,706.4	$ 304.8	$ (19.5)
Ending balance (in shares) at Mar. 31, 2021		64.8