Quarterly Financial and Market Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Quarterly Financial Information [Line Items]
Net sales	$ 511.7	$ 491.5	$ 491.3	$ 478.8	$ 483.5	$ 500.5	$ 522.6	$ 497.7	$ 1,973.3	$ 2,004.3	$ 1,861.2
Gross margin	142.2	135.6	139.9	134.1	135.6	135.7	150.3	143.0	551.8	564.6	532.8
Operating income	93.2	89.1	89.7	78.6	87.0	89.1	100.1	83.9	$ 350.6	$ 360.1	$ 332.4
Net income	$ 88.1	$ 69.7	$ 61.6	$ 64.6	$ 59.5	$ 68.2	$ 66.1	$ 56.0
Net income per common share:
Basic	$ 0.97	$ 0.77	$ 0.68	$ 0.71	$ 0.65	$ 0.74	$ 0.71	$ 0.60
Diluted	0.96	0.76	0.67	0.70	0.64	0.72	0.70	0.59
Maximum
Market price:
Common Stock Value during the Period	63.93	58.24	54.93	55.91	54.97	45.68	46.26	45.40
Minimum
Market price:
Common Stock Value during the Period	$ 57.43	$ 50.50	$ 49.20	$ 49.77	$ 42.04	$ 40.82	$ 39.15	$ 38.38