Commitments and Contingencies - Narrative (Details) $ in Millions				1 Months Ended		12 Months Ended
	May 16, 2017 USD ($) claimant	Jul. 17, 2015 USD ($) claimant	Mar. 06, 2015 class_action claimant	Apr. 30, 2017 USD ($) claimant	Jun. 30, 2015 USD ($) claimant	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2014 claimant	Dec. 31, 2012 operator	Dec. 14, 2018 class_action	May 31, 2018 class_action
Commitments and Contingencies Disclosure [Abstract]
Rent expense | $						$ 820	$ 716	$ 677
Pacer International
Loss Contingencies [Line Items]
Number of owner operators | operator										150
Number of claims heard by court | claimant		7	170		5				7
Amount claimed | $		$ 3			$ 1
Number of class actions related to remaining claimants | class_action			3
California Labor Commission
Loss Contingencies [Line Items]
Number of claims heard by court | claimant	5			4
Settlement amount awarded to other party | $	$ 1			$ 1
Last Mile Logistics Classifications Claims
Loss Contingencies [Line Items]
Number of class actions related to remaining claimants | class_action												4
Shareholder Litigation
Loss Contingencies [Line Items]
Number of class actions related to remaining claimants | class_action											2