Restructuring Charges - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 19	$ 21
Reserve Balance as of December 31, 2018	16	16
Transportation
Restructuring Cost and Reserve [Line Items]
Restructuring charges		12
Reserve Balance as of December 31, 2018	9	9
Transportation | Employee Severance
Restructuring Cost and Reserve [Line Items]
Reserve Balance as of December 31, 2018			$ 14
Logistics
Restructuring Cost and Reserve [Line Items]
Restructuring charges		6
Reserve Balance as of December 31, 2018	5	5
Logistics | Employee Severance
Restructuring Cost and Reserve [Line Items]
Reserve Balance as of December 31, 2018			5
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring charges		3
Reserve Balance as of December 31, 2018	$ 2	2
Corporate | Employee Severance
Restructuring Cost and Reserve [Line Items]
Reserve Balance as of December 31, 2018			$ 1
Direct Operating Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges		1
Selling, General and Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 20