Commitments and Contingent Liabilities - Narrative (Details)	1 Months Ended		9 Months Ended
	Oct. 31, 2018 purchaseRight order	Jul. 31, 2018 aircraft	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Long-term Purchase Commitment [Line Items]
Proceeds from sale leaseback transaction | $			$ 114,000,000	$ 0
Credit card processing agreements
Long-term Purchase Commitment [Line Items]
Holdbacks | $			$ 0		$ 0
Maximum limit of holdback (up to)			100.00%
B787-9 aircraft
Long-term Purchase Commitment [Line Items]
Number of aircraft under purchase agreements | aircraft		10
Number of aircraft with purchase rights | aircraft		10
General Electric GEnx engines | B787-9 aircraft
Long-term Purchase Commitment [Line Items]
Number of engines, firm order | purchaseRight	20
Number of engines, purchase rights | order	20
General Electric GEnx spare engines | B787-9 aircraft
Long-term Purchase Commitment [Line Items]
Number of spare engine purchase rights | purchaseRight	4