Condensed Consolidated Statements Of Changes in Shareholders’ Equity - USD ($) $ in Millions	Common Stock Including Additional Paid in Capital	Common Stock Subscribed, Unissued	Retained Earnings	AOCI Attributable to Parent	Noncontrolling Interest	Total
Balance at Dec. 31, 2018	$ 428.8		$ 678.1	$ (240.3)	$ 3.9	$ 870.5
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income			34.3		0.1	34.4
Other comprehensive income (loss)				5.7	0.1	5.8
Stock issued	8.8					8.8
Stock purchased	(5.5)				(0.3)	(5.8)
Advance payments		1.1				1.1
Dividends declared			(6.5)			(6.5)
Balance at Mar. 31, 2019	432.1	1.1	705.9	(234.6)	3.8	908.3
Balance at Dec. 31, 2018	428.8		678.1	(240.3)	3.9	870.5
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income						81.4
Other comprehensive income (loss)						11.4
Balance at Jun. 30, 2019	430.5	0.5	746.4	(229.1)	3.9	952.2
Balance at Mar. 31, 2019	432.1	1.1	705.9	(234.6)	3.8	908.3
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income			47.0			47.0
Other comprehensive income (loss)				5.5	0.1	5.6
Stock issued	3.7					3.7
Stock purchased	(5.3)					(5.3)
Advance payments		(0.6)				(0.6)
Dividends declared			(6.5)			(6.5)
Balance at Jun. 30, 2019	430.5	0.5	746.4	(229.1)	3.9	952.2
Balance at Dec. 31, 2019	449.5		694.0	(250.6)	4.9	897.8
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income			21.4		0.1	21.5
Other comprehensive income (loss)				(3.4)	(0.3)	(3.7)
Stock issued	9.4					9.4
Stock purchased	(4.2)				(0.1)	(4.3)
Advance payments		1.1				1.1
Dividends declared			(6.9)			(6.9)
Balance at Mar. 31, 2020	454.7	1.1	708.5	(254.0)	4.6	914.9
Balance at Dec. 31, 2019	449.5		694.0	(250.6)	4.9	897.8
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income						58.6
Other comprehensive income (loss)						6.1
Balance at Jun. 30, 2020	453.7	0.5	738.8	(244.4)	4.2	952.8
Balance at Mar. 31, 2020	454.7	1.1	708.5	(254.0)	4.6	914.9
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net Income			37.1			37.1
Other comprehensive income (loss)				9.6	0.2	9.8
Stock issued	3.6					3.6
Stock purchased	(4.6)				(0.6)	(5.2)
Advance payments		(0.6)				(0.6)
Dividends declared			(6.8)			(6.8)
Balance at Jun. 30, 2020	$ 453.7	$ 0.5	$ 738.8	$ (244.4)	$ 4.2	$ 952.8