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Common Stock and Stock-Based Awards Plans - Stock-Based Compensation (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares available for issuance	2.7		2.7
Compensation cost recognized for stock-based awards	$ 3.4	$ 2.7	$ 9.5	$ 8.5
Income tax benefit recognized in the income statement for stock-based awards	$ 0.8	$ 0.7	2.3	2.0
Total cash received as a result of stock option exercises			0.4	1.3
Tax benefit realized as a result of stock option exercises and the vesting of other share-based awards			1.8	1.7
Total intrinsic value of stock options exercised			$ 0.1	$ 0.4
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of options			10 years
Employee Awards [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Employee Awards [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Employee Awards [Member] \| Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Non-Employee Awards [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year