Revenues (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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
Disaggregation of Revenue [Line Items]
Revenue	$ 3,460,200	$ 3,657,600	$ 3,800,400	$ 3,116,400	$ 3,501,700	$ 3,788,000	$ 3,829,000	$ 3,244,200	$ 14,034,600	$ 14,362,900	$ 12,826,600
Earned rewards, expiration period									90 days
Trade accounts receivable	172,900				138,800				$ 172,900	138,800
Receivables related to contracts with customers
Disaggregation of Revenue [Line Items]
Trade accounts receivable	$ 96,000				$ 79,400				$ 96,000	79,400
Petroleum product sales, rack sales
Disaggregation of Revenue [Line Items]
Collection period									10 days
Renewable Identification Numbers (RINs) sales
Disaggregation of Revenue [Line Items]
Collection period									5 days
Minimum | Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Collection period									2 days
Maximum | Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Collection period									7 days
Difference between Revenue Guidance in Effect before and after Topic 606 | Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Revenue									$ 26,300	25,400
Difference between Revenue Guidance in Effect before and after Topic 606 | Petroleum product sales (at wholesale)
Disaggregation of Revenue [Line Items]
Revenue									165,600	171,200
Difference between Revenue Guidance in Effect before and after Topic 606 | Petroleum product sales
Disaggregation of Revenue [Line Items]
Revenue									$ 191,900	$ 196,500