Commitments and Contingencies - Airport Projects (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2010	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Airport Project
ACFO			$ 164	$ 1,768
Assets constructed for others, net	[1]		164	1,637
Depreciation and amortization			1,219	1,201	$ 1,218
Construction obligation			164	1,701
FLL Terminal
Airport Project
ACFO			0	313
Assets constructed for others, net	[1]		0	304
Construction obligation			0	308
LAX Terminal 1
Airport Project
ACFO			0	485
Assets constructed for others, net	[1]		0	459
Construction obligation			0	476
LAX Terminal 1.5
Airport Project
Expected total airport modernization project cost			479
Contractual Obligation			176
ACFO	[2]		164	99
Assets constructed for others, net	[1],[2]		164	99
Construction obligation	[2]		164	99
LFMP Terminal
Airport Project
Municipal bonds issued		$ 456
Municipal Bonds Principal Remaining			407
ACFO			0	545
Assets constructed for others, net	[1]		0	460
Construction obligation			0	502
Net Present Value of Principal Remaining			444
LFMP Parking Garage
Airport Project
ACFO			0	200
Assets constructed for others, net	[1]		0	200
Construction obligation			0	200
HOU International Terminal
Airport Project
ACFO	[3]		0	126
Assets constructed for others, net	[1],[3]		0	115
Construction obligation	[3]		$ 0	$ 116

[1] Net of accumulated depreciation.

[2] Project still in progress.

[3] Project completed in 2015 at Houston William P. Hobby Airport ("HOU").