Leases Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) aircraft_engine aircraft	Dec. 31, 2019 USD ($) a	Dec. 31, 2019 USD ($) a aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft held	151
Number of spare engines capitalized	16
Area of land | a		8.5	8.5
Land | $		$ 41,000,000.0	$ 41,000,000.0
Estimated time to complete construction		2 years
Operating lease not yet commenced, amount | $	$ 500,000
Operating lease not yet commenced, amount, year two | $	$ 0
Aircraft
Lessee, Lease, Description [Line Items]
Number of capitalized aircraft or engine purchased off lease	29
Spare Engines
Lessee, Lease, Description [Line Items]
Number of capitalized aircraft or engine purchased off lease	3
Minimum
Lessee, Lease, Description [Line Items]
Development in process estimated total costs | $	$ 200,000,000
Maximum
Lessee, Lease, Description [Line Items]
Development in process estimated total costs | $	$ 250,000,000
A320 Family | Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft capitalized	97
Airbus A319 [Member]
Lessee, Lease, Description [Line Items]
Number of aircraft to be purchased from finance lease			2
Aircraft
Lessee, Lease, Description [Line Items]
Number of delivered aircraft financed with debt	4
Number of previously leased aircraft or engine purchased off lease	2
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Operating leases, term	8 years
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term	18 years
Aircraft | A320 Family
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases	54
Spare Engines
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases | aircraft_engine	8
Number of spare engines purchased | aircraft_engine	2
Number Of spare engines returned | aircraft_engine	1
Other Leased Equipment and Property
Lessee, Lease, Description [Line Items]
Operating leases, term		99 years	99 years
Area of land | a		2.6	2.6
Other Leased Equipment and Property | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term	99 years
Leased Computer And Office Equipment | Minimum
Lessee, Lease, Description [Line Items]
Finance leases, term	3 years
Leased Computer And Office Equipment | Maximum
Lessee, Lease, Description [Line Items]
Finance leases, term	5 years
Third Party Lessor
Lessee, Lease, Description [Line Items]
Number of delivered leased aircraft	2