Major Customers and Concentration Of Risks	12 Months Ended
Dec. 31, 2018
Major Customers and Concentration Of Risks [Abstract]
Major Customers and Concentration Of Risks	Major Customers and Concentration of Risks Major Customers. No customer accounted for more than 10% of our consolidated revenues during 2016, 2017 or 2018. Concentration of Risks. We transport, store and distribute petroleum products for refiners, producers, marketers, traders and end users of those products. Our revenue producing activities are concentrated in the central U.S. Concentrations of customers may affect our overall credit risk as our customers may be similarly affected by changes in economic, regulatory or other factors. We generally secure transportation and storage revenue with warehouseman’s liens. We periodically evaluate the financial condition and creditworthiness of our customers and require additional security as we deem necessary. As of December 31, 2018, we had 1,868 employees, 948 of which were assigned to our refined products segment and concentrated in the central U.S. Approximately 24% of the 948 employees are represented by the United Steel Workers (“USW”) and were covered by a collective bargaining agreement that expired in January 2019 (see Note 19–Subsequent Events for additional information regarding the renegotiation of this agreement). At December 31, 2018, 160 of our employees were assigned to our crude oil segment and were concentrated in the central U.S., and none of these employees were covered by a collective bargaining agreement. There were 201 employees assigned to our marine storage segment at December 31, 2018, primarily in the Gulf and East Coast regions of the U.S., with approximately 14% of these employees represented by the International Union of Operating Engineers (“IUOE”) and covered by a collective bargaining agreement that expires in October 2020.

Major Customers and Concentration of Risks

Major Customers. No customer accounted for more than 10% of our consolidated revenues during 2016, 2017 or 2018.

Concentration of Risks. We transport, store and distribute petroleum products for refiners, producers, marketers, traders and end users of those products. Our revenue producing activities are concentrated in the central U.S. Concentrations of customers may affect our overall credit risk as our customers may be similarly affected by changes in economic, regulatory or other factors. We generally secure transportation and storage revenue with warehouseman’s liens. We periodically evaluate the financial condition and creditworthiness of our customers and require additional security as we deem necessary.

As of December 31, 2018, we had 1,868 employees, 948 of which were assigned to our refined products segment and concentrated in the central U.S. Approximately 24% of the 948 employees are represented by the United Steel Workers (“USW”) and were covered by a collective bargaining agreement that expired in January 2019 (see Note 19–Subsequent Events for additional information regarding the renegotiation of this agreement). At December 31, 2018, 160 of our employees were assigned to our crude oil segment and were concentrated in the central U.S., and none of these employees were covered by a collective bargaining agreement. There were 201 employees assigned to our marine storage segment at December 31, 2018, primarily in the Gulf and East Coast regions of the U.S., with approximately 14% of these employees represented by the International Union of Operating Engineers (“IUOE”) and covered by a collective bargaining agreement that expires in October 2020.