Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) segment state store	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary of Significant Accounting Policies
Number of reportable segments | segment	1
Accounts receivable due from employees to the Company	$ 900	$ 900
Allowance for doubtful supplier receivables	0	0
Replacement cost of inventory	3,670,000	3,470,000
LIFO inventory value in excess of replacement cost of inventory	55,800	31,000
Goodwill impairment	0	0
Impairment of long-lived assets	3,400	1,900	$ 11,400
Self-insurance reserves, current	109,199	79,079
Equity method investment in VIEs, net	19,500
Investment tax credit amount	170,500	8,500	19,400
Advertising expense, net	73,800	79,300	81,400
Total interest costs capitalized	10,200	13,000	$ 9,100
Deferred debt issuance costs, net of amortization	22,300	18,000
Original issuance discounts, net of accretion	5,100	3,500
Valuation allowance for deferred tax assets	0	0
Other assets
Summary of Significant Accounting Policies
Deferred debt issuance costs, net of amortization	$ 600	$ 1,100
U.S.
Summary of Significant Accounting Policies
Number of stores | store	5,594
Number of states, in which the Company operates | state	47
Mexico
Summary of Significant Accounting Policies
Number of stores | store	22
Loyalty Program Points [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Summary of Significant Accounting Policies
Deferred revenue, period expect to be recognized within	12 months
Loyalty Program Coupon [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Summary of Significant Accounting Policies
Deferred revenue, period expect to be recognized within	3 months