The following table reflects certain financial data for each segment for the periods indicated (in thousands): Three Months ended March 31, 2017 2018 Asphalt Terminalling Services Service revenue: Third-party revenue $ 13,223 $ 5,132 Related-party revenue 13,332 6,321 Lease revenue: Third-party revenue  9,458 Related-party revenue  7,702 Total revenue for reportable segment 26,555 28,613 Operating expense, excluding depreciation and amortization 12,319 13,333 Operating margin, excluding depreciation and amortization $ 14,236 $ 15,280 Total assets (end of period) $ 145,815 $ 170,473 Crude Oil Terminalling Services Service revenue: Third-party revenue $ 6,125 $ 4,585 Lease revenue: Third-party revenue  15 Total revenue for reportable segment 6,125 4,600 Operating expense, excluding depreciation and amortization 1,011 1,275 Operating margin, excluding depreciation and amortization $ 5,114 $ 3,325 Total assets (end of period) $ 70,518 $ 68,160 Three Months ended March 31, 2017 2018 Crude Oil Pipeline Services Service revenue: Third-party revenue $ 2,605 $ 2,061 Related-party revenue 310  Lease revenue: Third-party revenue  235 Product sales revenue: Third-party revenue 3,650 3,508 Total revenue for reportable segment 6,565 5,804 Operating expense, excluding depreciation and amortization 3,242 2,785 Operating expense (intersegment) 170 442 Cost of product sales 3,139 2,637 Operating margin, excluding depreciation and amortization $ 14 $ (60 ) Total assets (end of period) $ 145,351 $ 116,845 Crude Oil Trucking and Producer Field Services Service revenue: Third-party revenue $ 6,710 $ 5,540 Intersegment revenue 170 442 Lease revenue: Third-party revenue  97 Product sales revenue: Third-party revenue 385 6 Total revenue for reportable segment 7,265 6,085 Operating expense, excluding depreciation and amortization 7,268 6,375 Operating margin, excluding depreciation and amortization $ (3 ) $ (290 ) Total assets (end of period) $ 12,383 $ 6,113 Total operating margin, excluding depreciation and amortization (1) $ 19,3