Special Charges	12 Months Ended
Special Charges	Dec. 31, 2019
Special Charges and Credits [Abstract]
Special Charges	Special Charges Special Charges, Operating During the twelve months ended December 31, 2019, the Company recorded $0.7 million in special charges within operating expenses in the statement of operations related to the write-off of aircraft related credits resulting from the exchange of credits negotiated under the new purchase agreement with Airbus S.A.S. ("Airbus") executed during the fourth quarter of 2019. For additional information on the new purchase agreement with Airbus, refer to Note 18, Commitments and Contingencies. During the twelve months ended December 31, 2018, the Company negotiated and amended the collective bargaining agreement with the Air Line Pilots Association, International ("ALPA"), under the guidance of the National Mediation Board ("NMB"). In connection with the new agreement, the Company incurred a one-time ratification incentive of $80.2 million, including payroll taxes, and an $8.5 million adjustment related to other contractual provisions. As a result, the Company recorded $88.7 million in special charges within operating expenses in the statement of operations for the twelve months ended December 31, 2018. As of December 31, 2018, the Company had paid the full ratification incentive related to the Company's new collective bargaining agreement with its pilots. During the twelve months ended December 31, 2017, the Company purchased one engine and one aircraft which were previously financed under operating lease agreements. The purchase price of the one engine and one aircraft was $8.1 million and $20.0 million, respectively, comprised of a cash payment of $3.8 million and $12.6 million, respectively, and the non-cash application of maintenance and security deposits held by the previous lessor of $4.3 million and $7.4 million, respectively. The Company estimated the fair value of the engine and aircraft to be $3.1 million and $11.9 million, respectively, and has recorded the one purchased engine and one aircraft at fair value within flight equipment on the balance sheets. The Company determined the valuation of the engine and aircraft based on a third-party appraisal considering the condition of the engine and aircraft (a Level 3 measurement). The Company recognized $4.8 million and $7.9 million as a cost of terminating the lease within special charges on the statement of operations, respectively, made up of the excess of the purchase price paid over the fair value of the engine and the aircraft, less other non-cash items of $0.2 million and $0.2 million, respectively. Special Charges, Non-Operating During the twelve months ended December 31, 2019, the Company had no special charges, non-operating within other (income) expense in the statement of operations. During the twelve months ended December 31, 2018, the Company recorded $90.4 million, in special charges, non-operating within other (income) expense in the statement of operations. During the first quarter of 2018, the Company entered into an aircraft purchase agreement for the purchase of 14 A319 aircraft previously operated under operating leases by the Company. The aggregate gross purchase price for the 14 aircraft was $285.0 million, and the price for each aircraft at the time of the sale comprised a cash payment net of the amount of maintenance reserves and security deposits for such aircraft held by the applicable lessor pursuant to the lease for such aircraft. The contract was deemed a lease modification which resulted in a change of classification from operating leases to finance leases for the 14 aircraft. During the first quarter of 2018, the finance lease assets were recorded at the lower of cost or fair value of the aircraft within flight equipment on the Company's balance sheets. During the second quarter of 2018, the purchase of the 14 aircraft was completed and the obligation was accreted up to the net cash payment price with interest charges recognized in special charges, non-operating in the statement of operations. The Company determined the valuation of the aircraft based on third-party appraisals considering the condition of the aircraft (a Level 3 measurement). During the twelve months ended December 31, 2017, the Company had no special charges, non-operating.