Face/par value in contract for future debt financing commitments

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- Definition

Number of Aircraft with Secured Debt Financing Commitments Scheduled for Delivery

+ References

No definition available.

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- Definition

Number of Delivered Aircraft with Secured Debt Financing Commitments

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- Definition

Number of Trusts

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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Debt and Other Obligations (Details) $ in Thousands	1 Months Ended	3 Months Ended
Debt and Other Obligations (Details) $ in Thousands	Nov. 30, 2017 USD ($) aircraft trust	Mar. 31, 2018 USD ($) aircraft	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 1,748,100		$ 1,539,600
Less current maturities		136,500		115,430	$ 84,354
Less unamortized discounts		40,700		36,700
Total		1,570,926		1,387,498	$ 897,359
Repayments of debt obligations		18,700	$ 10,200
Equipment Notes, Series AA 2017-1 [Member]
Debt Instrument [Line Items]
Long-term debt		$ 171,000		37,500
Weighted-average interest rate		3.38%
Senior Loans [Member]
Debt Instrument [Line Items]
Long-term debt		$ 409,100		417,900
Weighted-average interest rate		4.10%	4.10%
Junior Loans [Member]
Debt Instrument [Line Items]
Long-term debt		$ 37,300		39,300
Weighted-average interest rate		6.90%	6.90%
Fixed Rate Loan [Member]
Debt Instrument [Line Items]
Long-term debt		$ 510,100		518,000
Weighted-average interest rate		3.83%	3.88%
Equipment Notes, Series A 2015-1 [Member]
Debt Instrument [Line Items]
Long-term debt		$ 408,600		408,600
Weighted-average interest rate		4.10%	4.10%
Equipment Notes, Series B 2015-1 [Member]
Debt Instrument [Line Items]
Long-term debt		$ 92,000		92,000
Weighted-average interest rate		4.45%	4.45%
Equipment Notes, Series A 2017-1 [Member]
Debt Instrument [Line Items]
Long-term debt		$ 57,000		12,500
Weighted-average interest rate		3.65%
Equipment Notes, Series B 2017-1 [Member]
Debt Instrument [Line Items]
Long-term debt		$ 63,000		$ 13,800
Weighted-average interest rate		3.80%
Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of pass-through trusts \| trust	3
Debt financing commitments	$ 420,500
Debt Instrument, Face Amount		$ 291,000
Enhanced Equipment Trust Certificate [Member] \| Equipment Notes, Series AA 2017-1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.375%
Enhanced Equipment Trust Certificate [Member] \| Equipment Notes, Series A 2017-1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.65%
Enhanced Equipment Trust Certificate [Member] \| Equipment Notes, Series B 2017-1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.80%
A320 [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of delivered aircraft with secured debt financing commitments \| aircraft		5
A321 [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of delivered aircraft with secured debt financing commitments \| aircraft		3
Airbus [Member] \| A320 [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	7
Airbus [Member] \| A321 [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	5
February 2018 To March 2018 [Member] \| Airbus [Member] \| A321 [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	5
December 2017 To January 2018 [Member] \| Airbus [Member] \| A320 [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	3
April 2018 To October 2018 [Member] \| Airbus [Member] \| A320 [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	4
2018 [Member] \| Airbus [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft		4
2018 [Member] \| Airbus [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft		4
Capital Addition Purchase Commitments [Member] \| Enhanced Equipment Trust Certificate [Member]
Debt Instrument [Line Items]
Debt financing commitments		$ 129,500