Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information [Line Items]
Net sales	$ 4,252.1	$ 4,502.6	$ 4,263.9	$ 3,939.3	$ 4,154.8	$ 4,422.6	$ 4,339.0	$ 3,754.1	$ 16,957.9	$ 16,670.5	$ 16,395.3
Cost of goods sold	4,030.3	4,267.6	4,050.8	3,720.9	3,924.3	4,176.0	4,100.1	3,545.9	16,069.6	15,746.3	15,527.8
Gross profit	221.8	235.0	213.1	218.4	230.5	246.6	238.9	208.2	888.3	924.2	867.5
Warehousing and distribution expenses	133.4	140.4	125.5	142.4	140.2	148.6	143.2	134.2	541.7	566.2	540.6
Selling, general and administrative expenses	61.2	57.3	59.8	63.9	63.1	61.8	64.6	65.9	242.2	255.4	245.1
Amortization of intangible assets	2.5	2.5	2.4	2.3	2.3	2.3	2.7	2.7	9.7	10.0	10.0
Total operating expenses	197.1	200.2	187.7	208.6	205.6	212.7	210.5	202.8	793.6	831.6	795.7
Income from operations	24.7	34.8	25.4	9.8	24.9	33.9	28.4	5.4	94.7	92.6	71.8
Interest expense, net	(2.1)	(2.1)	(2.8)	(3.5)	(3.6)	(4.2)	(3.2)	(3.4)	(10.5)	(14.4)	(13.7)
Foreign currency transaction (losses) gains, net	(0.2)	(0.5)	0.0	(0.2)	(0.5)	0.9	(1.0)	(0.2)	(0.9)	(0.8)	1.8
Income before income taxes	22.4	32.2	22.6	6.1	20.8	30.6	24.2	1.8	83.3	77.4	59.9
Income tax provision	(3.4)	(9.2)	(5.7)	(1.8)	(4.6)	(8.1)	(6.5)	(0.5)	(20.1)	(19.7)	(14.4)
Net income	$ 19.0	$ 23.0	$ 16.9	$ 4.3	$ 16.2	$ 22.5	$ 17.7	$ 1.3	$ 63.2	$ 57.7	$ 45.5
Basic net income per common share (in dollars per share)	$ 0.42	$ 0.51	$ 0.38	$ 0.09	$ 0.35	$ 0.49	$ 0.39	$ 0.03	$ 1.40	$ 1.26	$ 0.99
Diluted net income per common share (in dollars per share)	$ 0.42	$ 0.51	$ 0.38	$ 0.09	$ 0.35	$ 0.49	$ 0.38	$ 0.03	$ 1.39	$ 1.25	$ 0.99
Weighted-average common shares outstanding (in shares)	44.9	45.1	45.1	45.3	45.7	45.8	45.9	45.9	45.1	45.7	46.0
Weighted-average shares assuming dilution (in shares)	45.4	45.4	45.3	45.4	46.0	46.1	46.1	46.0	45.4	46.0	46.1
Excise taxes	$ 824.8	$ 888.3	$ 857.4	$ 770.3	$ 819.7	$ 884.1	$ 868.8	$ 768.7	$ 3,300.0	$ 3,300.0	$ 3,500.0
LIFO expense	9.2	5.4	8.3	7.8	5.9	7.3	7.4	7.0	30.7	27.6	25.2
Depreciation and amortization	17.7	16.5	16.7	15.7	15.1	14.9	15.5	15.4	66.6	60.9	59.5
Stock-based compensation	3.5	2.6	2.1	2.0	2.4	3.1	2.2	1.9	10.2	9.6	8.2
Capital expenditures	9.3	8.1	4.8	5.0	7.5	6.1	4.1	5.1	27.2	22.8	20.1
Cigarettes
Quarterly Financial Information [Line Items]
Net sales	2,835.0	3,000.2	2,892.6	2,582.7	2,711.2	2,880.0	2,834.0	2,467.5	11,310.5	10,892.7	10,974.5
Inventory holding gains	9.4	5.6	7.7	9.1	10.1	0.3	3.8	8.8	31.8	23.0
Food/non-food
Quarterly Financial Information [Line Items]
Net sales	$ 1,417.1	$ 1,502.4	$ 1,371.3	$ 1,356.6	1,443.6	1,542.6	1,505.0	1,286.6	5,647.4	5,777.8	5,420.8
Candy
Quarterly Financial Information [Line Items]
Net sales									1,004.0	1,039.0	$ 992.0
Inventory holding gains					$ 1.1	$ 5.8	$ 0.0	$ 0.0
United States | Cigarettes
Quarterly Financial Information [Line Items]
Inventory holding gains									29.8	21.3
United States | Candy
Quarterly Financial Information [Line Items]
Inventory holding gains										6.9
Canada | Cigarettes
Quarterly Financial Information [Line Items]
Inventory holding gains									$ 2.0	$ 1.7