Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Income from continuing operations	$ 65.4	$ 66.3	$ 57.3	$ 42.8	$ 48.3	$ 46.7	$ 43.5	$ 39.1	$ 231.8	$ 177.6	$ 149.7
Income from discontinued operations, net of income taxes	$ 19.6	$ 145.7	$ 6.9	$ 5.9	$ 7.1	$ 5.6	$ 5.3	$ 4.7	178.1	22.7	25.0
Income from continuing operations									$ 409.9	$ 200.3	$ 174.7
Weighted Average Number of Shares Outstanding Reconciliation
Weighted-average number of common shares outstanding - basic	52.0	52.7	53.2	53.0	52.8	52.5	52.5	52.8	52.7	52.7	52.8
Dilutive effect of common share equivalents									0.8	0.6	0.6
Weighted Average Number of Shares Outstanding, Diluted, Total	52.9	53.4	53.9	53.7	53.5	53.0	53.0	53.3	53.5	53.3	53.4
Continuing operations (in dollars per share)	$ 1.26	$ 1.26	$ 1.08	$ 0.81	$ 0.91	$ 0.89	$ 0.83	$ 0.74	$ 4.40	$ 3.37	$ 2.84
Discontinued operations (in dollars per share)	0.38	2.76	0.13	0.11	0.14	0.11	0.10	0.09	3.38	0.43	0.47
Earnings per share (in dollars per share)	1.64	4.02	1.21	0.92	1.05	1.00	0.93	0.83	7.78	3.80	3.31
Continuing operations (in dollars per share)	1.24	1.24	1.06	0.80	0.90	0.88	0.82	0.73	4.33	3.33	2.80
Discontinued operations (in dollars per share)	0.38	2.73	0.13	0.11	0.14	0.11	0.10	0.09	3.33	0.43	0.48
Earnings per share (in dollars per share)	$ 1.62	$ 3.97	$ 1.19	$ 0.91	$ 1.04	$ 0.99	$ 0.92	$ 0.82	$ 7.66	$ 3.76	$ 3.28