Leases Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Jun. 30, 2019 USD ($) aircraft	Sep. 30, 2019 USD ($) aircraft_engine aircraft	Sep. 30, 2019 USD ($) aircraft_engine aircraft	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease not yet commenced, amount		$ 500	$ 500
Operating lease not yet commenced, amount, year two		0	0
Finance lease obligations		$ 2,231	2,231
Gain on sale-leaseback transaction			100
Airbus A320 [Member]
Lessee, Lease, Description [Line Items]
Interest of lease liabilities, purchased aircraft previously leased			$ 300
Number of aircrafts purchased. previously leased | aircraft		4
Property, plant and equipment, purchase price, aircraft previously leased		$ 141,300
Spare Engines
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases | aircraft_engine		11	11
Aircraft | A320 Family [Member]
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases | aircraft		47	47
Fixed Maintenance Reserve Payments, Aircraft and Related Flight Equipment
Lessee, Lease, Description [Line Items]
Committed expenditures, remainder of 2019		$ 700	$ 700
Committed expenditures, 2020		2,600	2,600
Committed expenditures, 2021		2,600	2,600
Committed expenditures, 2022		2,700	2,700
Committed expenditures, 2023		2,500	2,500
Committed expenditures, 2024 and beyond		$ 500	$ 500
Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft financed under operating leases with a variable rate | aircraft		1	1
Number of delivered aircraft financed with debt | aircraft			2
Number of previously leased aircraft or engine purchased off lease | aircraft			5
Sale Leaseback Transaction, Number of Spare Aircraft Engines | aircraft			1
Finance lease obligations	$ 94,900
Capital leases, lessee balance sheet, assets by major class, flight equipment, gross	$ 140,500
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Operating leases, term		8 years	8 years
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term		18 years	18 years
Spare Engines
Lessee, Lease, Description [Line Items]
Number of previously leased aircraft or engine purchased off lease | aircraft			1
Number of spare engines purchased | aircraft_engine			2
Other Leased Equipment and Property | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term		30 years	30 years
Leased Computer And Office Equipment | Minimum
Lessee, Lease, Description [Line Items]
Finance leases, term		3 years	3 years
Leased Computer And Office Equipment | Maximum
Lessee, Lease, Description [Line Items]
Finance leases, term		5 years	5 years
Accounting Standards Update 2016-02 | Restatement Adjustment [Member]
Lessee, Lease, Description [Line Items]
Cumulative effect of Topic 842 adjustment				$ (5,500)
Capital Lease Obligations [Member] | Airbus A320 [Member]
Lessee, Lease, Description [Line Items]
Number of aircrafts to be purchased | aircraft	4
Third Party Lessor [Member]
Lessee, Lease, Description [Line Items]
Number of delivered leased aircraft | aircraft			5