Segment Data | Segment Data We aggregate our operating segments into two reportable segments: (i) pipelines and transportation and (ii) wholesale marketing and terminalling: • The assets and investments reported in the pipeline and transportation segment provide crude oil gathering and crude oil, intermediate and refined products transportation and storage services to Delek Holdings' refining operations and independent third parties. • The wholesale marketing and terminalling segment provides marketing services for the refined products output of the Delek Holdings' refineries, engages in wholesale activity at our terminals and terminals owned by third parties, whereby we purchase light product for sale and exchange to third parties, and provides terminalling services at our refined products terminals to independent third parties and Delek Holdings. Our operating segments adhere to the accounting policies used for our consolidated financial statements. Our operating segments are managed separately because each segment requires different industry knowledge, technology and marketing strategies. Decisions concerning the allocation of resources and assessment of operating performance are made based on this segmentation. Management measures the operating performance of each of its reportable segments based on segment contribution margin. Segment contribution margin is defined as net revenues less cost of materials and other and operating expenses, excluding depreciation and amortization. The following is a summary of business segment operating performance as measured by contribution margin for the periods indicated: (in thousands) Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Pipelines and Transportation Net revenues: Affiliate $ 65,664 $ 61,394 $ 128,712 $ 99,897 Third party 4,771 2,032 6,698 11,496 Total pipelines and transportation 70,435 63,426 135,410 111,393 Cost of materials and other 14,346 11,182 27,425 17,280 Operating expenses (excluding depreciation and amortization) 10,858 9,731 21,030 21,187 Segment contribution margin $ 45,231 $ 42,513 $ 86,955 $ 72,926 Capital spending $ 1,531 $ 417 $ 7,376 $ 863 Wholesale Marketing and Terminalling Net revenues: Affiliate (1) $ 23,058 $ 26,235 $ 56,204 $ 94,431 Third party 74,985 27,976 129,777 75,214 Total wholesale marketing and terminalling 98,043 54,211 185,981 169,645 Cost of materials and other 74,349 32,710 142,441 127,905 Operating expenses (excluding depreciation and amortization) 4,623 2,718 8,507 6,006 Segment contribution margin $ 19,071 $ 18,783 $ 35,033 $ 35,734 Capital spending $ 1,060 $ 235 $ 3,014 $ 2,818 Consolidated Net revenues: Affiliate $ 88,722 $ 87,629 $ 184,916 $ 194,328 Third party 79,756 30,008 136,475 86,710 Total Consolidated 168,478 117,637 321,391 281,038 Cost of materials and other 88,695 43,892 169,866 145,185 Operating expenses (excluding depreciation and amortization presented below) 15,481 12,449 29,537 27,193 Contribution margin $ 64,302 $ 61,296 121,988 108,660 General and administrative expenses 6,077 4,721 10,937 10,851 Depreciation and amortization 9,967 8,694 20,706 14,993 Other operating income, net (136) — (219) (107) Operating income $ 48,394 $ 47,881 $ 90,564 $ 82,923 Capital spending $ 2,591 $ 652 $ 10,390 $ 3,681 (1) Affiliate revenue for the wholesale marketing and terminalling segment is presented net of amortization expense related to a customer contract intangible asset. See Note 4 for additional information. The following table summarizes the total assets for each segment as of June 30, 2021 and December 31, 2020 (in thousands). Assets for each segment include property, plant and equipment, equity method investments, intangible assets and inventory. June 30, 2021 December 31, 2020 Pipelines and transportation $ 699,588 $ 723,317 Wholesale marketing and terminalling 214,750 206,918 Other 21,138 26,182 Total assets $ 935,476 $ 956,417 Property, plant and equipment and accumulated depreciation as of June 30, 2021 and depreciation expense by reporting segment for the three and six months ended June 30, 2021 were as follows (in thousands): Pipelines and Transportation Wholesale Marketing and Terminalling Consolidated Property, plant and equipment $ 587,821 $ 114,002 $ 701,823 Less: accumulated depreciation (192,077) (54,995) (247,072) Property, plant and equipment, net $ 395,744 $ 59,007 $ 454,751 Depreciation expense for the three months ended June 30, 2021 $ 8,035 $ 1,932 $ 9,967 Depreciation expense for the six months ended June 30, 2021 $ 16,862 $ 3,844 $ 20,706 In accordance with ASC 360, Property, Plant & Equipment |