Summary of Significant Accounting Policies - Debt Issuance Costs, Claims Liabilities and Insurance Recoverables, and Risks and Concentrations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies [Line Items]
Self insurance gross obligation, long-term	$ 38,200,000	$ 36,100,000
Self insurance gross obligation, short-term	22,500,000	20,400,000
Self insurance liabilities net of insurance recoverables, long-term	22,800,000	21,700,000
Self insurance liabilities net of insurance recoverables, short-term	$ 18,400,000	$ 17,300,000
Net, sales | Cigarettes | Product Concentration Risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, percentage	66.70%	65.30%	66.90%
Product purchase | Altria Group, Inc. | Supplier Concentration Risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, percentage	33.00%	32.00%	33.00%
Product purchase | R.J. Reynolds Tobacco Company | Supplier Concentration Risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, percentage	25.00%	22.00%	23.00%
Gross profit | Cigarettes | Product Concentration Risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, percentage	25.20%	23.00%	26.00%
Murphy USA | Net, sales | Customer Concentration Risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, percentage	13.90%	12.50%	11.90%
Workers' Compensation, General and Auto Liabilities Program
Summary of Significant Accounting Policies [Line Items]
Self-insurance pre-claim limit, amount	$ 500,000
Health and Welfare Program
Summary of Significant Accounting Policies [Line Items]
Self-insurance pre-claim limit, amount	$ 400,000