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Stock-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	May 21, 2019
Stock-based Compensation Arrangement by Stock-based Payment Award [Line Items]
Number of shares authorized (in shares)					4,236,959
Shares available for issuance (in shares)	3,136,192		3,136,192
Stock-based compensation cost	$ 2.6	$ 3.1	$ 6.7	$ 7.2
Total unrecognized compensation cost related to non-vested share-based compensation arrangements	$ 14.1		$ 14.1
Compensation cost not yet recognized, period for recognition			1 year 7 months 6 days
Performance-Based Restricted Stock Units
Stock-based Compensation Arrangement by Stock-based Payment Award [Line Items]
Granted, number of shares (in shares)			154,363	154,511
Grants in period, weighted average grant date fair value (in dollars per share)			$ 25.48	$ 29.90
2010 LTIP \| Restricted Stock Units
Stock-based Compensation Arrangement by Stock-based Payment Award [Line Items]
Granted, number of shares (in shares)			280,325	230,235
Grants in period, weighted average grant date fair value (in dollars per share)			$ 25.38	$ 29.67