Description of Business and Presentation of Financial Statements - Impact of Adoption, Cumulative Effect on Financials (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable: Product and transportation	$ 669,978	$ 651,332	$ 659,530
Inventories: Crude oil and refined products	1,318,728	1,414,662	1,409,538
Accounts payable	1,194,082	1,228,131	1,220,795
Deferred income tax liability	679,899	644,822	647,785
Retained earnings	$ 3,544,830	$ 3,339,168	3,346,615
Prior to Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable: Product and transportation			659,530
Inventories: Crude oil and refined products			1,409,538
Accounts payable			1,220,795
Deferred income tax liability			647,785
Retained earnings			3,346,615
Increase (Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable: Product and transportation			(8,198)
Inventories: Crude oil and refined products			5,124
Accounts payable			7,336
Deferred income tax liability			(2,963)
Retained earnings			$ (7,447)