Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) store state segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Summary of Significant Accounting Policies
Number of reportable segments | segment	1
Accounts receivable due from employees to the Company	$ 900	$ 1,100
Allowance for doubtful supplier receivables	0	0
Replacement cost of inventory	3,470,000	3,200,000
LIFO inventory value in excess of replacement cost of inventory	31,000	107,300
Goodwill impairment	0	0
Impairment of long-lived assets	1,900	11,400
Self-insurance reserves, current	79,079	77,012
Advertising expense, net	79,300	81,400	$ 83,700
Total interest costs capitalized	13,000	9,100	$ 8,500
Deferred debt issuance costs, net of amortization	18,000	17,100
Original issuance discounts, net of accretion	3,500	4,300
Valuation allowance for deferred tax assets	0	0
Operating lease, right-of-use assets	1,928,369	0
Operating lease, liability	1,971,358
Adoption of ASU 2016-02 [Member]
Summary of Significant Accounting Policies
Cumulative effective adjustment to opening Retained earnings	1,400
Operating lease, right-of-use assets	1,900,000
Operating lease, liability	$ 2,000,000
U.S.
Summary of Significant Accounting Policies
Number of stores | store	5,439
Number of states, in which the Company operates | state	47
Mexico
Summary of Significant Accounting Policies
Number of stores | store	21
Other Assets [Member]
Summary of Significant Accounting Policies
Deferred debt issuance costs, net of amortization	$ 1,100	$ 1,500
Loyalty Program Points [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
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]: 2020-01-01
Summary of Significant Accounting Policies
Deferred revenue, period expect to be recognized within	3 months