Commitments and Contingencies (Future Minimum Rental Payments Under All Non-Cancelable Operating Leases) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Property Subject to or Available for Operating Lease [Line Items]
2018	$ 44,580
2019	41,753
2020	36,220
2021	27,596
2022	23,764
2023 and thereafter	115,937
Total minimum lease obligations	289,850
Office Space
Property Subject to or Available for Operating Lease [Line Items]
2018	3,972
2019	3,951
2020	3,984
2021	3,233
2022	2,693
2023 and thereafter	4,696
Total minimum lease obligations	22,529
Transportation equipment
Property Subject to or Available for Operating Lease [Line Items]
2018	25,871
2019	25,209
2020	23,403
2021	17,818
2022	16,317
2023 and thereafter	55,614
Total minimum lease obligations	164,232
Terminals and Tanks
Property Subject to or Available for Operating Lease [Line Items]
2018	14,737
2019	12,593
2020	8,833
2021	6,545
2022	4,754
2023 and thereafter	55,627
Total minimum lease obligations	$ 103,089