Condensed Consolidated Statements of Changes in Shareholders’ Equity - USD ($) $ in Millions	Total	Common Stock	Common Stock Subscribed, Unissued	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance at Dec. 31, 2017	$ 761.6	$ 387.7	$ 0.0	$ 619.9	$ (250.1)	$ 4.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21.2			21.1		0.1
Other comprehensive income (loss)	2.2				2.3	(0.1)
Stock issued	8.4	8.4
Stock purchased	(4.9)	(4.7)				(0.2)
Advance payments	1.1		1.1
Dividends declared	(5.9)			(5.9)
Balance at Mar. 31, 2018	784.5	391.4	1.1	635.9	(247.8)	3.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASC 606, net of tax	0.8			0.8
Balance at Dec. 31, 2018	870.5	428.8	0.0	678.1	(240.3)	3.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34.4			34.3		0.1
Other comprehensive income (loss)	5.8				5.7	0.1
Stock issued	8.8	8.8
Stock purchased	(5.8)	(5.5)				(0.3)
Advance payments	1.1		1.1
Dividends declared	(6.5)			(6.5)
Balance at Mar. 31, 2019	$ 908.3	$ 432.1	$ 1.1	$ 705.9	$ (234.6)	$ 3.8