Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Other Capital	Other Capital Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2020			76.8
Beginning balance at Dec. 31, 2020	$ 220.4		$ 7.7	$ 562.1		$ (64.4)	$ (57.4)		$ (227.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18.1						18.1
Amortization of net actuarial losses and prior service costs, net of income taxes	11.5								11.5
Adjustment to dividends paid	13.3						13.3
Settlement of debt (in shares)			2.6
Settlement of debt	(3.8)		$ 0.3	(4.1)
Repurchase of shares for withholding taxes and option costs under equity plans	(4.0)			(4.0)
Stock-based compensation and shares issued under equity plans (in shares)			0.2
Stock-based compensation and shares issued under equity plans	8.4			8.4
Ending balance (in shares) at Mar. 31, 2021			79.6
Ending balance at Mar. 31, 2021	263.9		$ 8.0	562.4		(64.4)	(26.0)		(216.1)
Beginning balance (in shares) at Dec. 31, 2020			76.8
Beginning balance at Dec. 31, 2020	220.4		$ 7.7	562.1		(64.4)	(57.4)		(227.6)
Ending balance (in shares) at Dec. 31, 2021			80.1
Ending balance at Dec. 31, 2021	$ 523.3	$ (6.6)	$ 8.0	578.1	$ (5.6)	(64.4)	102.6	$ (1.0)	(101.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2020-06 [Member]
Net income	$ 27.8						27.8
Amortization of net actuarial losses and prior service costs, net of income taxes	5.2								5.2
Repurchase of shares for withholding taxes and option costs under equity plans (in shares)			(0.1)
Repurchase of shares for withholding taxes and option costs under equity plans	(4.3)			(4.3)
Stock-based compensation and shares issued under equity plans (in shares)			0.3
Stock-based compensation and shares issued under equity plans	4.5			4.5
Ending balance (in shares) at Mar. 31, 2022			80.3
Ending balance at Mar. 31, 2022	$ 549.9		$ 8.0	$ 572.7		$ (64.4)	$ 129.4		$ (95.8)