Leases Narrative (Details) $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($) aircraft_engine aircraft	Jun. 30, 2019 USD ($) 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	$ 96,382	$ 96,382
Spare Engines
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases | aircraft_engine	11	11
Aircraft | A320 Family
Lessee, Lease, Description [Line Items]
Number of leased assets financed under operating leases | aircraft	46	46
Fixed Maintenance Reserve Payments, Aircraft and Related Flight Equipment
Lessee, Lease, Description [Line Items]
Committed expenditures, remainder of 2019	$ 1,400	$ 1,400
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		1
Finance lease obligations	$ 94,900	$ 94,900
Capital leases, lessee balance sheet, assets by major class, flight equipment, gross	$ 140,500	$ 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
Lessee, Lease, Description [Line Items]
Number of aircrafts to be purchased | aircraft	4
Property, plant and equipment, purchase price	$ 141,300
Third Party Lessor [Member]
Lessee, Lease, Description [Line Items]
Number of delivered leased aircraft | aircraft		5