Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock Issued	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Dec. 31, 2018		30,771,244
Beginning Balance at Dec. 31, 2018	$ 557.9	$ 3.1	$ 71.1	$ 608.2	$ (124.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17.4			17.4
Other comprehensive (loss), net of tax	0.7				0.7
Dividends declared	(13.6)			(13.6)
Restricted stock issuances, net (in shares)		141,021
Stock-based employee compensation expense	0.9		0.9
Stock issued to directors as compensation (in shares)		1,696
Stock issued to directors as compensation			0.0
Purchases and retirement of common stock (in shares)		(24,372)
Purchases and retirement of common stock	(0.9)			(0.9)
Ending Balance at Mar. 31, 2019	562.1	$ 3.1	72.0	610.8	(123.8)
Ending Balance (in shares) at Mar. 31, 2019		30,889,589
Beginning Balance (in shares) at Dec. 31, 2019		30,896,661
Beginning Balance at Dec. 31, 2019	597.7	$ 3.1	78.8	638.4	(122.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22.5			22.5
Other comprehensive (loss), net of tax	(15.7)				(15.7)
Dividends declared	(13.7)			(13.7)
Restricted stock issuances, net (in shares)		320,005
Stock-based employee compensation expense	2.1		2.1
Stock issued to directors as compensation (in shares)		1,130
Stock issued to directors as compensation	0.1		0.1
Purchases and retirement of common stock (in shares)		(25,274)
Purchases and retirement of common stock	(1.0)			(1.0)
Ending Balance at Mar. 31, 2020	$ 592.0	$ 3.1	$ 81.0	$ 646.2	$ (138.3)
Ending Balance (in shares) at Mar. 31, 2020		31,192,522