Revenue - Air Traffic Liability Breakout (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Revenue Recognition and Deferred Revenue [Abstract]
ATL - PAX Revenue and Ancillary PAX Services	$ 2,635	$ 1,898
ATL - Loyalty Program	2,948	2,667
Air Traffic Liability Total	$ 5,583	$ 4,565	$ 5,023	$ 4,221

Air Traffic Liability Passenger Revenue and Ancillary Passenger Services

No definition available.

Name:	luv_AirTrafficLiabilityPassengerRevenueandAncillaryPassengerServices
Namespace Prefix:	luv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant