Consolidated Statements Of Changes in Shareholders’ Equity - USD ($) $ in Millions	Common Stock Including Additional Paid in Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Balance at Dec. 31, 2017	$ 387.7		$ 619.9	$ (250.1)	$ 4.1		$ 761.6
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income			143.3		0.4		143.7
Other comprehensive income (loss)				9.8	(0.3)		9.5
Stock issued	17.8						17.8
Stock purchased	(15.7)				(0.3)		(16.0)
Dividends declared	39.0		(85.9)				(46.9)
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2018		$ 0.8				$ 0.8
Balance at Dec. 31, 2018	428.8		678.1	(240.3)	3.9		870.5
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Increase in retained earnings							678.1
Net income			144.5		0.4		144.9
Other comprehensive income (loss)				(10.3)	0.1		(10.2)
Stock issued	18.5				0.8		19.3
Stock purchased	(19.2)				(0.3)		(19.5)
Dividends declared	21.4		(128.6)				(107.2)
Balance at Dec. 31, 2019	449.5		694.0	(250.6)	4.9		897.8
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Increase in retained earnings							694.0
Net income			121.8		0.3		122.1
Other comprehensive income (loss)				3.9	0.2		4.1
Stock issued	19.1						19.1
Stock purchased	(16.5)				(0.9)		(17.4)
Dividends declared			(90.7)				(90.7)
Balance at Dec. 31, 2020	$ 452.1		$ 725.1	$ (246.7)	$ 4.5		935.0
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Increase in retained earnings							$ 725.1