Background and Basis of Presentation - EPS (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) primary_operation $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of primary operations | primary_operation			2
Earnings (Loss) Per Basic Common Share
Income from continuing operations	$ 14.4	$ 12.9	$ 39.8	$ 24.3
Amounts attributable to participating securities	(0.1)	(0.1)	(0.2)	(0.3)
Income from continuing operations available to common stockholders	14.3	12.8	39.6	24.0
Loss from discontinued operations	0.0	(0.8)	0.0	(0.8)
Net income available to common stockholders	$ 14.3	$ 12.0	$ 39.6	$ 23.2
Weighted-average basic shares outstanding (in shares) | shares	16,837,000	16,849,000	16,850,000	16,848,000
Continuing operations (in usd per share) | $ / shares	$ 0.85	$ 0.76	$ 2.35	$ 1.43
Discontinued operations (in usd per share) | $ / shares	0	(0.05)	0	(0.05)
Basic (in usd per share) | $ / shares	$ 0.85	$ 0.71	$ 2.35	$ 1.38
Earnings (Loss) Per Diluted Common Share
Income from continuing operations	$ 14.4	$ 12.9	$ 39.8	$ 24.3
Amounts attributable to participating securities	(0.1)	(0.1)	(0.2)	(0.3)
Income from continuing operations available to common stockholders	14.3	12.8	39.6	24.0
Loss from discontinued operations	0.0	(0.8)	0.0	(0.8)
Net income available to common stockholders	$ 14.3	$ 12.0	$ 39.6	$ 23.2
Weighted-average diluted shares
Weighted-average basic shares outstanding (in shares) | shares	16,837,000	16,849,000	16,850,000	16,848,000
Add: Assumed incremental shares under stock compensation plans (in shares) | shares	68,000	139,000	60,000	136,000
Weighted-average diluted shares (in shares) | shares	16,905,000	16,988,000	16,910,000	16,984,000
Continuing operations (in usd per share) | $ / shares	$ 0.84	$ 0.75	$ 2.33	$ 1.41
Discontinued operations (in usd per share) | $ / shares	0	(0.05)	0	(0.05)
Diluted (in usd per share) | $ / shares	$ 0.84	$ 0.70	$ 2.33	$ 1.36
Potentially dilutive stock-based compensation awards excluded from computation of dilutive common shares (in shares) | shares	231,471	106,789	231,199	143,853