Commitments and Contingent Liabilities - Narrative (Details)	1 Months Ended			6 Months Ended
	Jul. 28, 2020 USD ($) aircraft	Oct. 31, 2018 purchaseRight order	Jul. 31, 2018 aircraft	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Long-term Purchase Commitment [Line Items]
Proceeds from sale leaseback transaction | $				$ 4,350,000
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
A321neo aircraft | Subsequent Event [Member] | Transaction For Aircraft
Long-term Purchase Commitment [Line Items]
Proceeds from sale leaseback transaction | $	$ 114,000,000.0
Sale lease-back transaction, number of aircraft | aircraft	2
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