Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales		$ 4,154.8	$ 4,422.6	$ 4,339.0	$ 3,754.1	$ 4,089.7	$ 4,273.2	$ 4,226.5	$ 3,805.9	$ 16,670.5	$ 16,395.3	$ 15,687.6
Cost of goods sold		3,924.3	4,176.0	4,100.1	3,545.9	3,872.7	4,039.4	4,009.6	3,606.1	15,746.3	15,527.8	14,895.9
Gross profit		230.5	246.6	238.9	208.2	217.0	233.8	216.9	199.8	924.2	867.5	791.7
Warehousing and distribution expenses		140.2	148.6	143.2	134.2	136.4	137.6	134.3	132.3	566.2	540.6	504.1
Selling, general and administrative expenses		63.1	61.8	64.6	65.9	61.2	58.8	61.7	63.4	255.4	245.1	224.3
Amortization of intangible assets		2.3	2.3	2.7	2.7	2.4	2.5	2.6	2.5	10.0	10.0	8.5
Total operating expenses		205.6	212.7	210.5	202.8	200.0	198.9	198.6	198.2	831.6	795.7	736.9
Income from operations		24.9	33.9	28.4	5.4	17.0	34.9	18.3	1.6	92.6	71.8	54.8
Interest expense, net		(3.6)	(4.2)	(3.2)	(3.4)	(3.1)	(3.4)	(3.4)	(3.8)	(14.4)	(13.7)	(11.0)
Foreign currency transaction (losses) gains, net		(0.5)	0.9	(1.0)	(0.2)	1.3	(0.4)	0.5	0.4	(0.8)	1.8	1.8
Pension termination settlement (Note 12)	$ (17.2)									0.0	0.0	(17.2)
Income before income taxes		20.8	30.6	24.2	1.8	15.2	31.1	15.4	(1.8)	77.4	59.9	28.4
(Provision) benefit for income taxes (Note 11)		(4.6)	(8.1)	(6.5)	(0.5)	(3.1)	(7.4)	(4.4)	0.5	(19.7)	(14.4)	5.1
Net income		$ 16.2	$ 22.5	$ 17.7	$ 1.3	$ 12.1	$ 23.7	$ 11.0	$ (1.3)	$ 57.7	$ 45.5	$ 33.5
Earnings per share (Note 13):
Basic (in dollars per share)		$ 0.35	$ 0.49	$ 0.39	$ 0.03	$ 0.26	$ 0.52	$ 0.24	$ (0.03)	$ 1.26	$ 0.99	$ 0.72
Diluted (in dollars per share)		$ 0.35	$ 0.49	$ 0.38	$ 0.03	$ 0.26	$ 0.51	$ 0.24	$ (0.03)	$ 1.25	$ 0.99	$ 0.72
Weighted-average shares outstanding (Note 13):
Basic (in shares)		45.7	45.8	45.9	45.9	45.7	45.9	46.0	46.2	45.7	46.0	46.3
Diluted (in shares)		46.0	46.1	46.1	46.0	46.0	46.2	46.1	46.2	46.0	46.1	46.4