Contingencies and Commitments - Narrative (Details) $ in Millions		4 Months Ended	9 Months Ended
	May 02, 2019 lawsuit	Jul. 07, 2020 plaintiff	Aug. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 04, 2020 passenger
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	2
Reserve funds			$ 27
Customer deposits			200
Estimate of reserve funds, per month			65
Estimate of reserve funds, maximum			$ 600
Number of passengers, COVID-19 contracted allegations | passenger					2
Subsequent Event
Loss Contingencies [Line Items]
Escrow deposit				$ 136
Minimum
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff		100