Background and Basis of Presentation - EPS (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) segment $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of primary operations | segment			2
Potentially dilutive stock-based compensation awards excluded from computation of dilutive common shares | shares	0	90,000	47,000	45,000
Earnings (Loss) Per Basic Common Share
Income from continuing operations	$ 16.4	$ 13.5	$ 57.0	$ 46.0
Amounts attributable to participating securities	(0.2)	(0.2)	(0.6)	(0.5)
Income from continuing operations available to common stockholders	16.2	13.3	56.4	45.5
Loss from discontinued operations, net of income taxes	0.0	(7.4)	(0.4)	(6.9)
Amounts attributable to participating securities	0.0	0.1	0.0	0.1
Net income available to common stockholders	$ 16.2	$ 6.0	$ 56.0	$ 38.7
Weighted-average basic shares outstanding (in shares) | shares	16,771,000	16,738,000	16,774,000	16,737,000
Basic earnings (loss) per share
Continuing operations (in dollars per share) | $ / shares	$ 0.97	$ 0.79	$ 3.36	$ 2.72
Discontinued operations (in dollars per share) | $ / shares	0.00	(0.43)	(0.02)	(0.41)
Basic (in dollars per share) | $ / shares	$ 0.97	$ 0.36	$ 3.34	$ 2.31
Earnings (Loss) Per Diluted Common Share
Income from continuing operations	$ 16.4	$ 13.5	$ 57.0	$ 46.0
Amounts attributable to participating securities	(0.2)	(0.2)	(0.6)	(0.5)
Income from continuing operations available to common stockholders	16.2	13.3	56.4	45.5
Loss from discontinued operations, net of income taxes	0.0	(7.4)	(0.4)	(6.9)
Amounts attributable to participating securities	0.0	0.1	0.0	0.1
Net income available to common stockholders	$ 16.2	$ 6.0	$ 56.0	$ 38.7
Weighted-average basic shares outstanding (in shares) | shares	16,771,000	16,738,000	16,774,000	16,737,000
Add: Assumed incremental shares under stock compensation plans (in shares) | shares	317,000	211,000	294,000	254,000
Weighted-average diluted shares (in shares) | shares	17,088,000	16,949,000	17,068,000	16,991,000
Diluted earnings (loss) per share
Continuing operations (in dollars per share) | $ / shares	$ 0.95	$ 0.78	$ 3.30	$ 2.68
Discontinued operations (in dollars per share) | $ / shares	0.00	(0.43)	(0.02)	(0.40)
Diluted (in dollars per share) | $ / shares	$ 0.95	$ 0.35	$ 3.28	$ 2.28