Allegiant Travel (ALGT) 10-Q 3 Aug 18 2018 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 01, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Allegiant Travel CO
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		16,163,533
Amendment Flag	false
Entity Central Index Key	1,362,468
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well Known Seasoned Issuer	Yes
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2

Consolidated Balance Sheets (Cu

Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.001
CURRENT ASSETS
Cash and cash equivalents	$ 28,981	$ 59,449
Restricted cash	13,253	11,190
Short-term investments	343,180	352,681
Accounts receivable	24,184	71,057
Expendable parts, supplies and fuel, net	20,419	17,647
Prepaid expenses	34,447	23,931
Other current assets	829	5,320
TOTAL CURRENT ASSETS	465,293	541,275
Property and equipment, net	1,746,707	1,512,415
Long-term investments	56,358	78,570
Deferred major maintenance, net	36,957	31,326
Deposits and other assets	20,190	16,571
TOTAL ASSETS:	2,325,505	2,180,157
CURRENT LIABILITIES
Accounts payable	27,473	20,108
Accrued liabilities	124,326	105,127
Air traffic liability	236,932	204,299
Current maturities of long-term debt and capital lease obligations, net of related costs	144,392	214,761
TOTAL CURRENT LIABILITIES	533,123	544,295
Long-term debt and capital lease obligations, net of current maturities and related costs	992,322	950,131
Deferred income taxes	144,254	119,013
Other noncurrent liabilities	11,138	13,407
TOTAL LIABILITIES:	1,680,837	1,626,846
SHAREHOLDERS' EQUITY
Common stock, par value $.001	23	23
Treasury stock	(607,025)	(605,655)
Additional paid in capital	263,034	253,840
Accumulated other comprehensive loss, net	(2,473)	(2,840)
Retained earnings	991,109	907,943
TOTAL EQUITY:	644,668	553,311
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY:	$ 2,325,505	$ 2,180,157

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cash dividends declared per share:	$ 0.70	$ 0.70	$ 1.40	$ 1.40
OPERATING REVENUE:
Passenger revenue	$ 405,572	$ 367,250	$ 802,343	$ 715,086
Third party products	17,799	14,304	28,124	27,046
Fixed fee contract revenue	7,653	11,029	18,209	22,289
Other revenue	5,756	9,261	13,548	17,434
Total operating revenue	436,780	401,844	862,224	781,855
OPERATING EXPENSES:
Aircraft fuel	122,454	85,387	228,481	170,049
Salary and benefits	101,645	92,221	214,608	188,519
Station operations	41,553	38,998	79,137	70,830
Maintenance and repairs	24,611	28,645	43,881	58,740
Depreciation and amortization	29,833	30,129	57,983	60,678
Sales and marketing	18,348	13,492	37,426	26,822
Aircraft lease rentals	75	2,400	96	2,564
Other	24,039	24,777	46,422	44,129
Total operating expenses	362,558	316,049	708,034	622,331
OPERATING INCOME	74,222	85,795	154,190	159,524
OTHER (INCOME) EXPENSE:
Interest expense	13,156	8,889	25,880	17,291
Interest income	(1,927)	(1,475)	(3,834)	(2,739)
Other, net	50	493	290	854
Total other expense	11,179	6,921	21,756	13,698
INCOME BEFORE INCOME TAXES	63,043	78,874	132,434	145,826
PROVISION FOR INCOME TAXES	13,027	29,836	27,225	54,437
NET INCOME	$ 50,016	$ 49,038	$ 105,209	$ 91,389
Earnings per share to common shareholders:
Basic	$ 3.10	$ 2.98	$ 6.53	$ 5.52
Earnings Per Share, Diluted	$ 3.10	$ 2.97	$ 6.52	$ 5.51
Shares used for computation:
Basic	15,939,000	16,198,000	15,898,000	16,290,000
Diluted	15,945,000	16,220,000	15,914,000	16,317,000

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income	$ 50,016	$ 49,038	$ 105,209	$ 91,389
Other comprehensive income (loss):
Change in available for sale securities, net of tax	113	(2)	(843)	222
Foreign currency translation adjustments	113	(215)	214	(298)
Change in derivatives, net of tax	1,260	(581)	996	(1,085)
Total other comprehensive income (loss)	1,486	(798)	367	(1,161)
TOTAL COMPREHENSIVE INCOME	$ 51,502	$ 48,240	$ 105,576	$ 90,228

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Adjustments to reconcile net income to net cash provided by operating activities:
Net income	$ 105,209	$ 91,389
Depreciation and amortization	57,983	60,678
(Gain) loss on aircraft and other equipment disposals	(1,491)	4,901
Provision for obsolescence of expendable parts, supplies and fuel	493	1,753
Amortization of deferred financing costs	744	775
Share-based compensation expense	6,106	7,249
Deferred income taxes	25,241	52,153
Changes in certain assets and liabilities:
Decrease in accounts receivable	46,873	16,572
Increase in prepaid expenses	(10,516)	(9,476)
Increase in accounts payable	7,631	2,263
Increase in accrued liabilities	20,859	10,382
Increase in air traffic liability	32,633	42,394
Change in deferred major maintenance	(7,841)	(14,331)
Other, net	(689)	(3,782)
Net cash provided by operating activities	283,235	262,920
INVESTING ACTIVITIES:
Purchase of investment securities	(168,923)	(242,895)
Proceeds from maturities of investment securities	199,294	154,334
Aircraft pre-delivery deposits	0	(63,468)
Purchase of property and equipment, including capitalized interest	(187,456)	(118,846)
Other investing activities	(1,468)	1,352
Net cash used in investing activities	(158,553)	(269,523)
FINANCING ACTIVITIES:
Cash dividends paid to shareholders	(22,605)	(23,204)
Proceeds from the issuance of debt	10,797	134,540
Repurchase of common stock	(2,994)	(84,940)
Principal payments on debt and capital lease obligations	(142,399)	(64,876)
Other financing activities	4,114	188
Net cash used in financing activities	(153,087)	(38,292)
Net change in cash, cash equivalents, and restricted cash	(28,405)	(44,895)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT BEGINNING OF PERIOD	70,639	76,358
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT END OF PERIOD	42,234	31,463
CASH PAYMENTS FOR:
Interest paid, net of amount capitalized	24,370	16,001
Income taxes paid, net of (refunds)	$ (41,284)	$ (13,967)

Consolidated Statements of Cas6

Consolidated Statements of Cash Flows (Parenthetical) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Consolidated Statements of Cash Flows (Parenthetical) [Abstract]
Cash and cash equivalents	$ 28,981	$ 59,449	$ 20,040
Restricted cash	13,253	11,190	11,423
TOTAL CASH, CASH EQUIVALENTS AND RESTRICTED CASH	$ 42,234	$ 70,639	$ 31,463	$ 76,358

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements include the accounts of Allegiant Travel Company (the “Company”) and its majority-owned operating subsidiaries. The Company has no independent operations, and all guarantees of the Company's publicly held debt are full and unconditional and joint and several. Any subsidiaries of the parent company other than the subsidiary guarantors are minor. All intercompany balances and transactions have been eliminated. These unaudited consolidated financial statements reflect all normal recurring adjustments which management believes are necessary to present fairly the financial position, results of operations, and cash flows of the Company for the respective periods presented. Certain reclassifications have been made to prior year financial statements to conform to classifications used in the current year. Certain information and footnote disclosures normally included in the annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") have been omitted pursuant to the rules and regulations of the Securities and Exchange Commission for Form 10-Q. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements of the Company and notes thereto included in the annual report of the Company on Form 10-K for the year ended December 31, 2017 and filed with the Securities and Exchange Commission. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from these estimates. Recent Accounting Pronouncements Standards Effective in Future Years In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02 related to leases. This standard will require leases with durations greater than twelve months to be recognized on the balance sheet as a lease liability and a corresponding right-of-use asset, and is effective for interim and annual reporting periods beginning after December 15, 2018 with early adoption permitted. The Company will adopt this standard effective January 1, 2019. The Company has not completed the assessment of this new standard and believes adoption will have a significant impact on its consolidated balance sheets but is not expected to significantly change the recognition, measurement or presentation of associated expenses within the consolidated statements of income or cash flows. Recently Adopted Standards In August 2016, the FASB issued ASU 2016-15, which amends the guidance in Accounting Standards Codification ("ASC") 230 on the classification of certain cash receipts and payments in the statement of cash flows. The Company adopted this standard effective January 1, 2018. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220)." This standard provides an option to reclassify stranded tax effects within accumulated other comprehensive income (loss) ("AOCI") to retained earnings. The Company adopted this standard effective January 1, 2018 and a one-time effect of $0.6 million was reclassified from AOCI to retained earnings as of June 30, 2018 as a result of this adoption. In 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), (the "New Revenue Standard"). Under this ASU and subsequently issued amendments, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration received. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted this standard using the full retrospective transition method effective January 1, 2018 and recast prior year results. See Note 2, "Revenue Recognition" for more information on the financial impact of this adoption. Under the New Revenue Standard, revenue for all air-related ancillary fees that are directly related to ticket revenue, such as seat fees and baggage fees, are no longer considered distinct performance obligations separate from passenger travel and are reclassified into passenger revenue. These are deemed part of the single performance obligation of providing passenger transportation. While the adoption of the New Revenue Standard did not have a significant effect on earnings, $167.6 million and $322.3 million of air-related ancillary fees for the three and six months ended June 30, 2018 , respectively, are now classified as passenger revenue. The adoption of the New Revenue Standard resulted in a net reduction to air traffic liability at December 31, 2017 of $5.9 million . This change resulted from the recognition of breakage revenue on issuance of credit vouchers that are expected to expire unused. In addition, recognition of revenues for fees associated with flight changes or cancellations are now deferred rather than being recognized at the time the fee is incurred. The Company recognizes revenue from the co-brand credit card program on the deferral method. Bank of America has issued The Allegiant World Mastercard® in which points are earned and awarded to cardholders in exchange for consideration received under an agreement with a seven year scheduled duration expiring in 2023. Under this arrangement, the Company identified the following deliverables: travel points to be awarded (the travel component), use of the Company’s brand and access to its member lists, and certain other advertising and marketing elements (collectively the marketing component). Consideration received from the Company’s co-brand agreement is allocated between the two components based on the relative selling price of each deliverable. The Company applies a level of management judgment and estimation in determining the best estimate of selling price for each deliverable by considering multiple inputs and methods including, but not limited to, the redemption value of points awarded, discounted cash flows, brand value, volume discounts, published selling prices, number of points to be awarded and number of points to be redeemed.

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure	Property and Equipment Property and equipment (in thousands): As of June 30, 2018 As of December 31, 2017 Flight equipment, including pre-delivery deposits $ 1,785,184 $ 1,539,433 Computer hardware and software 131,661 123,675 Other property and equipment 151,802 125,855 Total property and equipment 2,068,647 1,788,963 Less accumulated depreciation and amortization (321,940 ) (276,548 ) Property and equipment, net $ 1,746,707 $ 1,512,415

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt and capital lease obligations (in thousands): As of June 30, 2018 As of December 31, 2017 Fixed-rate debt and capital lease obligations due through 2030 $ 577,452 $ 465,462 Variable-rate debt due through 2027 559,262 699,430 Total long-term debt and capital lease obligations, net of related costs 1,136,714 1,164,892 Less current maturities, net of related costs 144,392 214,761 Long-term debt and capital lease obligations, net of current maturities and related costs $ 992,322 $ 950,131 Weighted average fixed-interest rate on debt 5.4 % 5.4 % Weighted average variable-interest rate on debt 4.0 % 3.3 % Maturities of long-term debt and capital lease obligations for the remainder of 2018 and for the next five years and thereafter, in the aggregate, are: remaining in 2018 - $92.5 million ; 2019 - $555.4 million ; 2020 - $103.5 million ; 2021 - $76.6 million ; 2022 - $49.2 million ; and $259.5 million thereafter. Secured Debt During the six months ended June 30, 2018 , the Company borrowed $10.8 million under a loan agreement secured by various ground equipment. The notes bear interest at a fixed rate of 4.2 percent per year, payable in monthly installments over five years. Senior Secured Revolving Credit Facility In 2015, the Company, through a wholly owned subsidiary, entered into a senior secured revolving credit facility under which it was entitled to borrow up to $56.0 million . In March 2018, the Company paid off the balance of the facility and amended it to increase the borrowing limit to $81.0 million . The amended facility has a term of 24 months and is based on the value of Airbus A320 Series aircraft which the Company may choose to place in the collateral pool. There was no balance under this facility as of June 30, 2018 . See Note 10, "Subsequent Events," for more information on the revolving credit facility. General Unsecured Senior Notes In June 2014, the Company completed an offering of $300.0 million aggregate principal amount of senior unsecured obligations (the "Notes") which will mature in July 2019. In December 2016, the Company completed an offering of an additional $150.0 million principal amount of these notes, which were issued at a price of 101.5 percent of the principal amount, plus accrued interest from July 15, 2016. The Notes bear interest at a rate of 5.5 percent per year, payable in cash semi-annually, on January 15th and July 15th of each year. The indenture pursuant to which the Notes were issued includes operating and financial restrictions on the Company. These restrictions limit or restrict, among other things, the Company’s ability and the ability of its restricted subsidiaries to (i) incur additional indebtedness; (ii) incur liens; (iii) make restricted payments (including paying dividends on, redeeming, repurchasing or retiring capital stock); (iv) make investments; and (v) consolidate, merge or sell all or substantially all of its assets. These covenants are subject to various exceptions and qualifications under the terms of the indenture. As of December 31, 2017 and June 30, 2018 , the Company exceeded the consolidated total leverage ratio limit, which could affect the ability to make restricted payments in future periods after exhaustion of various exceptions. However, it is not expected that this will have any impact on the restricted payments routinely made in the ordinary course of business. The calculation is made on a quarterly basis based on the trailing 12 months. Capital Leases The Company has capital lease obligations related to aircraft, which significantly impacted our recognized assets and liabilities as of June 30, 2018 , but did not result in any significant cash receipts or cash payments during the quarter.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value, Measurement Inputs, Disclosure	Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received by selling an asset or paid to transfer a liability in an orderly transaction between market participants. Accounting standards pertaining to fair value measurements establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than Level 1 inputs that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own assumptions. The Company uses the market approach valuation technique to determine fair value for investment securities. The assets classified as Level 1 consist of money market funds for which original cost approximates fair value. The assets classified as Level 2 consist of commercial paper, municipal debt securities, federal agency debt securities, US Treasury Bonds, and corporate debt securities, which are valued using quoted market prices or alternative pricing sources including transactions involving identical or comparable assets and models utilizing market observable inputs. The Company has no investment securities classified as Level 3. For those assets classified as Level 2 that are not in active markets, the Company obtains fair value from pricing sources using quoted market prices for identical or comparable instruments, and uses pricing models which include all significant observable inputs: maturity dates, issue dates, settlement dates, benchmark yields, reported trades, broker-dealer quotes, issue spreads, benchmark securities, bids, offers and other market related data. These inputs are observable or can be derived from, or corroborated by, observable market data for substantially the full term of the asset. The fair value of the Company's derivative instrument is determined using standard valuation models. The significant inputs used in these models are readily available in public markets or can be derived from observable market transactions and therefore have been classified as Level 2. Inputs used in these standard valuation models for derivative instruments include the applicable exchange and interest rates. Financial instruments measured at fair value on a recurring basis (in thousands): As of June 30, 2018 As of December 31, 2017 Total Level 1 Level 2 Total Level 1 Level 2 Cash equivalents Commercial paper $ 9,952 $ — $ 9,952 $ 27,910 $ — $ 27,910 Municipal debt securities 5,325 — 5,325 2,782 — 2,782 Money market funds 115 115 — 1,297 1,297 — Total cash equivalents 15,392 115 15,277 31,989 1,297 30,692 Short-term Commercial paper 141,091 — 141,091 108,678 — 108,678 Corporate debt securities 116,804 — 116,804 107,878 — 107,878 Municipal debt securities 53,143 — 53,143 101,290 — 101,290 Federal agency debt securities 30,718 — 30,718 31,428 — 31,428 US Treasury Bonds 1,424 — 1,424 3,407 — 3,407 Total short-term 343,180 — 343,180 352,681 — 352,681 Long-term Corporate debt securities 43,363 — 43,363 60,396 — 60,396 Federal agency debt securities 10,022 — 10,022 5,775 — 5,775 US Treasury Bonds 2,973 — 2,973 2,994 — 2,994 Derivative instruments 21 — 21 282 — 282 Municipal debt securities — — — 9,405 — 9,405 Total long-term 56,379 — 56,379 78,852 — 78,852 Total financial instruments $ 414,951 $ 115 $ 414,836 $ 463,522 $ 1,297 $ 462,225 The fair value of the Company’s publicly held long-term debt is determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets; therefore, the Company has categorized its publicly held debt as Level 2. Remaining debt is not publicly held, and the Company has determined the estimated fair value of these notes to be Level 3, as certain inputs used to determine the fair value are unobservable and, therefore, could be sensitive to changes in inputs. The Company utilizes the discounted cash flow method to estimate the fair value of Level 3 debt. Carrying value and estimated fair value of long-term debt, including current maturities and without reduction for related costs (in thousands): As of June 30, 2018 As of December 31, 2017 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Hierarchy Level Publicly held debt $ 450,893 $ 453,147 $ 451,321 $ 462,604 2 Non-publicly held debt 589,357 526,887 719,681 660,065 3 Total long-term debt $ 1,040,250 $ 980,034 $ 1,171,002 $ 1,122,669 Due to the short-term nature, carrying amounts of cash, cash equivalents, restricted cash, accounts receivable and accounts payable approximate fair value.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Stockholders' Equity	Shareholders’ Equity The Company is authorized by the Board of Directors to acquire up to $100.0 million of its stock through open market purchases under its share repurchase program. As repurchase authority is used, the Board of Directors has, to date, authorized additional expenditures for share repurchases. Share repurchases consisted of the following: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Shares repurchased (not in thousands) (1) None 589,057 None 604,497 Average price per share NA $ 142.16 NA $ 142.66 Total (in thousands) None $ 83,740 None $ 86,240 (1) Share amounts shown above include only open market repurchases and do not include shares withheld from employees for tax withholding obligations related to restricted stock vestings. During the six months ended June 30, 2018 , the Company declared and paid recurring cash dividends of $1.40 per share, or $22.6 million .

Earnings per Share

Earnings per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic and diluted earnings per share are computed pursuant to the two-class method. Under this method, the Company attributes net income to two classes: common stock and unvested restricted stock. Unvested restricted stock awards granted to employees under the Company’s Long-Term Incentive Plan are considered participating securities as they receive non-forfeitable rights to cash dividends at the same rate as common stock. Diluted net income per share is calculated using the more dilutive of the two methods. Under both methods, the exercise of employee stock options is assumed using the treasury stock method. The assumption of vesting of restricted stock, however, differs: 1. Assume vesting of restricted stock using the treasury stock method. 2. Assume unvested restricted stock awards are not vested, and allocate earnings to common shares and unvested restricted stock awards using the two-class method. For the three and six months ended June 30, 2018 , the second method, which assumes unvested awards are not vested, was used in the computation because it was more dilutive than the first method. The following table sets forth the computation of net income per share, on a basic and diluted basis, for the periods indicated (share count and dollar amounts other than per-share amounts in table are in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Basic: Net income $ 50,016 $ 49,038 $ 105,209 $ 91,389 Less net income allocated to participating securities (659 ) (789 ) (1,427 ) (1,482 ) Net income attributable to common stock $ 49,357 $ 48,249 $ 103,782 $ 89,907 Earnings per share, basic $ 3.10 $ 2.98 $ 6.53 $ 5.52 Weighted-average shares outstanding 15,939 16,198 15,898 16,290 Diluted: Net income $ 50,016 $ 49,038 $ 105,209 $ 91,389 Less net income allocated to participating securities (658 ) (789 ) (1,425 ) (1,480 ) Net income attributable to common stock $ 49,358 $ 48,249 $ 103,784 $ 89,909 Earnings per share, diluted $ 3.10 $ 2.97 $ 6.52 $ 5.51 Weighted-average shares outstanding 15,939 16,198 15,898 16,290 Dilutive effect of stock options and restricted stock 44 71 63 92 Adjusted weighted-average shares outstanding under treasury stock method 15,983 16,269 15,961 16,382 Participating securities excluded under two-class method (38 ) (49 ) (47 ) (65 ) Adjusted weighted-average shares outstanding under two-class method 15,945 16,220 15,914 16,317 For the three and six months ended June 30, 2018 , anti-dilutive shares excluded from the calculation of earnings per share were 1,379 and 607 shares (not in thousands), respectively.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies As of June 30, 2018 , the Company had firm commitments to purchase 11 Airbus A320 aircraft. In addition, the Company has entered into lease agreements for an additional 13 Airbus A320 aircraft, three of which have been delivered and are in service, and one of which has been delivered but was not in service as of June 30, 2018 . The remaining nine aircraft are currently scheduled to be delivered in the second half of 2018 and first quarter of 2019. Future minimum fixed payments for the Company's commitments related to the acquisition of aircraft (including aircraft lease obligations), airport fees under use and lease agreements, and other operating lease obligations are as follows as of June 30, 2018 (in thousands): As of June 30, 2018 Remaining in 2018 $ 79,148 2019 123,164 2020 67,422 2021 26,288 2022 23,569 Thereafter 150,598 Total commitments $ 470,189 Contingencies The Company is subject to certain legal and administrative actions it considers routine to its business activities. The Company believes the ultimate outcome of any pending legal or administrative matters will not have a material adverse impact on its financial position, liquidity or results of operations.

Related Party

Related Party	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related Party Transactions During the three and six months ended June 30, 2018 , the Company made no payments to related parties. Entities owned or controlled by the Company's Chairman and CEO have been paid for the building of corporate training content. During the three and six months ended June 30, 2017 , the Company made payments to these entities of $0.2 million . No further payments are expected.

Revenue Recognition Revenue Rec

Revenue Recognition Revenue Recognition	6 Months Ended
	Jun. 30, 2018
Revenue Recognition [Abstract]
Revenue from Contract with Customer [Text Block]	Revenue Recognition Certain prior period amounts have been recast to conform to the adoption of the New Revenue Standard as shown in the tables below. Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 (in thousands, except per share As Previously Reported Current Presentation As Previously Reported Current Presentation data) Adjustments Adjustments Income Statement: Passenger revenue (1) $ 220,615 $ 146,635 $ 367,250 $ 432,713 $ 282,373 $ 715,086 Air-related charges 145,405 (145,405 ) — 276,970 (276,970 ) — Sales and marketing 12,861 631 13,492 22,859 3,963 26,822 Income tax provision 29,800 36 29,836 54,279 158 54,437 Net income 48,475 563 49,038 90,107 1,282 91,389 Diluted earnings per share $ 2.94 $ 0.03 $ 2.97 $ 5.43 $ 0.08 $ 5.51 (1) Passenger revenue previously reported as Scheduled service revenue. December 31, 2017 As Previously Current (in thousands) Reported Adjustments Presentation Balance Sheet: Air traffic liability $ 210,184 $ (5,885 ) $ 204,299 Deferred income taxes 118,492 521 119,013 Retained earnings 902,579 5,364 907,943 Passenger Revenue Passenger revenue is primarily composed of passenger ticket sales, credit voucher breakage, seat fees, baggage fees, and other travel-related services performed in conjunction with a passenger’s flight, as well as co-brand point redemptions as outlined below: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2018 2017 2018 2017 Scheduled service $ 235,746 $ 220,811 $ 474,267 $ 435,075 Air-related ancillary charges 167,630 145,887 322,347 279,111 Co-brand redemptions 2,196 552 5,729 900 Total passenger revenue $ 405,572 $ 367,250 $ 802,343 $ 715,086 Scheduled service Passenger tickets . The Company provides scheduled air transportation on limited-frequency, nonstop flights predominantly between under-served cities and popular leisure destinations. Sales of passenger tickets not yet flown are recorded in air traffic liability. Passenger revenue is recognized when transportation is provided or when ticket voucher breakage occurs. The contract term of passenger tickets is 12 months and revenue associated with future travel will principally be recognized within this time frame. $187.8 million was recognized into passenger revenue during the six months ended June 30, 2018 that was recorded in the air traffic liability balance of $204.3 million at December 31, 2017. Credit voucher breakage . The Company estimates the value of vouchers that will expire unused and recognizes revenue at the time the credit voucher is issued. Air-related Air-related revenue is primarily composed of services performed in conjunction with a passenger's flight and include baggage fees, the use of the Company’s website to purchase scheduled service transportation, advance seat assignments, and other services. Revenue for these services is recognized when the related transportation service is provided. Prior to the adoption of the New Revenue Standard, the majority of these fees were classified separately as Air-related ancillary charges. Co-brand redemption In relation to the travel component of the contract with Bank of America, the Company has a performance obligation to provide cardholders with points to be used for future travel award redemptions. Therefore, consideration received from Bank of America related to the travel component is deferred based on its relative selling price and is recognized into passenger revenue when the points are redeemed and the transportation is provided. The following table presents the activity of the current and non-current point liabilities (in thousands): 2018 Balance at January 1 $ 8,903 Points awarded 6,898 Points redeemed (5,730 ) Balance at June 30 $ 10,071 As of June 30, 2018 , $6.9 million of the current points liability is reflected in Accrued liabilities and represents our current estimate of revenue to be recognized in the next twelve months based on historical trends, with the remaining balance reflected in Other noncurrent liabilities expected to be recognized into revenue in periods thereafter. See below, Third Party Products revenue, for discussion of the marketing component. Third Party Products Third party products revenue is generated from the sale of hotel rooms, rental cars, ticket attractions and co-brand marketing revenue. Revenue from the sale of hotel rooms, rental cars, and ticket attractions is recognized at the time the product is utilized, such as the time a purchased hotel room is occupied. The Company follows the accounting standards for principal versus agent revenue arrangements to determine the amount of revenue to be recognized for each element of a bundled sale involving air-related charges and third party products, in addition to airfare. Revenue from the sale of third party products is recorded net (treatment as an agent) of amounts paid to wholesale providers, travel agent commissions, and transaction costs. Pursuant to the co-brand agreement with Bank of America, the Company has various performance obligations collectively referred to as the marketing component. These obligations consist of use of the Company’s brand and access to its member lists, and certain other advertising and marketing elements. The marketing component is recorded as third party products revenue in the period in which points are awarded to the credit card holders. Fixed Fee Contract Revenue Fixed fee contract revenue consists of agreements to provide charter service on a year-round and ad hoc basis. Fixed fee contract revenue is recognized when the transportation is provided. Other Revenue Other revenue is generated from leased aircraft, engines, and other miscellaneous sources. Lease revenue is recognized ratably over the lease term. Accounts Receivable Accounts receivable, reflected on the accompanying consolidated balance Sheets, primarily consist of amounts due from credit card companies associated with passenger revenue. These receivables are short-term, generally settled within a few days of sale. Bad debt expense, which occurs in the form of credit card chargebacks, was not material in any period presented. Taxes and Fees Various taxes and fees, assessed on the sale of tickets to customers, are collected by the Company serving as an agent, and remitted to taxing authorities. These taxes and fees are not included as revenue in the Company’s consolidated statements of income and are recorded as a liability until remitted to the appropriate taxing authority.

Subsequent Events (Notes)

Subsequent Events (Notes)	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events In July 2018, the Company drew down $46.9 million under its senior secured revolving credit facility. The notes for the amounts borrowed under the facility bear interest at a floating rate based on LIBOR and are due on March 31, 2020. Also in July 2018, the Company also borrowed $34.5 million under a loan agreement secured by one Airbus A320 series aircraft. The note bears interest at a floating rate based on LIBOR and will be payable in quarterly installments through July 2028.

Summary of Significant Accoun17

Summary of Significant Accounting Policies - (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements include the accounts of Allegiant Travel Company (the “Company”) and its majority-owned operating subsidiaries. The Company has no independent operations, and all guarantees of the Company's publicly held debt are full and unconditional and joint and several. Any subsidiaries of the parent company other than the subsidiary guarantors are minor. All intercompany balances and transactions have been eliminated. These unaudited consolidated financial statements reflect all normal recurring adjustments which management believes are necessary to present fairly the financial position, results of operations, and cash flows of the Company for the respective periods presented. Certain reclassifications have been made to prior year financial statements to conform to classifications used in the current year. Certain information and footnote disclosures normally included in the annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") have been omitted pursuant to the rules and regulations of the Securities and Exchange Commission for Form 10-Q. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements of the Company and notes thereto included in the annual report of the Company on Form 10-K for the year ended December 31, 2017 and filed with the Securities and Exchange Commission. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from these estimates.
New Accounting Pronouncements	Recent Accounting Pronouncements Standards Effective in Future Years In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02 related to leases. This standard will require leases with durations greater than twelve months to be recognized on the balance sheet as a lease liability and a corresponding right-of-use asset, and is effective for interim and annual reporting periods beginning after December 15, 2018 with early adoption permitted. The Company will adopt this standard effective January 1, 2019. The Company has not completed the assessment of this new standard and believes adoption will have a significant impact on its consolidated balance sheets but is not expected to significantly change the recognition, measurement or presentation of associated expenses within the consolidated statements of income or cash flows. Recently Adopted Standards In August 2016, the FASB issued ASU 2016-15, which amends the guidance in Accounting Standards Codification ("ASC") 230 on the classification of certain cash receipts and payments in the statement of cash flows. The Company adopted this standard effective January 1, 2018. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220)." This standard provides an option to reclassify stranded tax effects within accumulated other comprehensive income (loss) ("AOCI") to retained earnings. The Company adopted this standard effective January 1, 2018 and a one-time effect of $0.6 million was reclassified from AOCI to retained earnings as of June 30, 2018 as a result of this adoption. In 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), (the "New Revenue Standard"). Under this ASU and subsequently issued amendments, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration received. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted this standard using the full retrospective transition method effective January 1, 2018 and recast prior year results. See Note 2, "Revenue Recognition" for more information on the financial impact of this adoption. Under the New Revenue Standard, revenue for all air-related ancillary fees that are directly related to ticket revenue, such as seat fees and baggage fees, are no longer considered distinct performance obligations separate from passenger travel and are reclassified into passenger revenue. These are deemed part of the single performance obligation of providing passenger transportation. While the adoption of the New Revenue Standard did not have a significant effect on earnings, $167.6 million and $322.3 million of air-related ancillary fees for the three and six months ended June 30, 2018 , respectively, are now classified as passenger revenue. The adoption of the New Revenue Standard resulted in a net reduction to air traffic liability at December 31, 2017 of $5.9 million . This change resulted from the recognition of breakage revenue on issuance of credit vouchers that are expected to expire unused. In addition, recognition of revenues for fees associated with flight changes or cancellations are now deferred rather than being recognized at the time the fee is incurred. The Company recognizes revenue from the co-brand credit card program on the deferral method. Bank of America has issued The Allegiant World Mastercard® in which points are earned and awarded to cardholders in exchange for consideration received under an agreement with a seven year scheduled duration expiring in 2023. Under this arrangement, the Company identified the following deliverables: travel points to be awarded (the travel component), use of the Company’s brand and access to its member lists, and certain other advertising and marketing elements (collectively the marketing component). Consideration received from the Company’s co-brand agreement is allocated between the two components based on the relative selling price of each deliverable. The Company applies a level of management judgment and estimation in determining the best estimate of selling price for each deliverable by considering multiple inputs and methods including, but not limited to, the redemption value of points awarded, discounted cash flows, brand value, volume discounts, published selling prices, number of points to be awarded and number of points to be redeemed.

Summary of Significant Accoun18

Summary of Significant Accounting Policies Disaggregation of Revenue (Tables)	6 Months Ended
	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Disaggregation of Revenue [Table Text Block]	Passenger revenue is primarily composed of passenger ticket sales, credit voucher breakage, seat fees, baggage fees, and other travel-related services performed in conjunction with a passenger’s flight, as well as co-brand point redemptions as outlined below: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2018 2017 2018 2017 Scheduled service $ 235,746 $ 220,811 $ 474,267 $ 435,075 Air-related ancillary charges 167,630 145,887 322,347 279,111 Co-brand redemptions 2,196 552 5,729 900 Total passenger revenue $ 405,572 $ 367,250 $ 802,343 $ 715,086

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	Property and equipment (in thousands): As of June 30, 2018 As of December 31, 2017 Flight equipment, including pre-delivery deposits $ 1,785,184 $ 1,539,433 Computer hardware and software 131,661 123,675 Other property and equipment 151,802 125,855 Total property and equipment 2,068,647 1,788,963 Less accumulated depreciation and amortization (321,940 ) (276,548 ) Property and equipment, net $ 1,746,707 $ 1,512,415

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Summary of Long-Term Debt	Long-term debt and capital lease obligations (in thousands): As of June 30, 2018 As of December 31, 2017 Fixed-rate debt and capital lease obligations due through 2030 $ 577,452 $ 465,462 Variable-rate debt due through 2027 559,262 699,430 Total long-term debt and capital lease obligations, net of related costs 1,136,714 1,164,892 Less current maturities, net of related costs 144,392 214,761 Long-term debt and capital lease obligations, net of current maturities and related costs $ 992,322 $ 950,131 Weighted average fixed-interest rate on debt 5.4 % 5.4 % Weighted average variable-interest rate on debt 4.0 % 3.3 %

Long-Term Debt Schedule of Matu

Long-Term Debt Schedule of Maturities of Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Schedule of Maturities of Long-Term Debt [Abstract]
Schedule of Maturities of Long-term Debt	Maturities of long-term debt and capital lease obligations for the remainder of 2018 and for the next five years and thereafter, in the aggregate, are: remaining in 2018 - $92.5 million ; 2019 - $555.4 million ; 2020 - $103.5 million ; 2021 - $76.6 million ; 2022 - $49.2 million ; and $259.5 million thereafter.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value On a Recurring Basis	Financial instruments measured at fair value on a recurring basis (in thousands): As of June 30, 2018 As of December 31, 2017 Total Level 1 Level 2 Total Level 1 Level 2 Cash equivalents Commercial paper $ 9,952 $ — $ 9,952 $ 27,910 $ — $ 27,910 Municipal debt securities 5,325 — 5,325 2,782 — 2,782 Money market funds 115 115 — 1,297 1,297 — Total cash equivalents 15,392 115 15,277 31,989 1,297 30,692 Short-term Commercial paper 141,091 — 141,091 108,678 — 108,678 Corporate debt securities 116,804 — 116,804 107,878 — 107,878 Municipal debt securities 53,143 — 53,143 101,290 — 101,290 Federal agency debt securities 30,718 — 30,718 31,428 — 31,428 US Treasury Bonds 1,424 — 1,424 3,407 — 3,407 Total short-term 343,180 — 343,180 352,681 — 352,681 Long-term Corporate debt securities 43,363 — 43,363 60,396 — 60,396 Federal agency debt securities 10,022 — 10,022 5,775 — 5,775 US Treasury Bonds 2,973 — 2,973 2,994 — 2,994 Derivative instruments 21 — 21 282 — 282 Municipal debt securities — — — 9,405 — 9,405 Total long-term 56,379 — 56,379 78,852 — 78,852 Total financial instruments $ 414,951 $ 115 $ 414,836 $ 463,522 $ 1,297 $ 462,225
Fair Value, Liabilities Measured on Recurring Basis	Carrying value and estimated fair value of long-term debt, including current maturities and without reduction for related costs (in thousands): As of June 30, 2018 As of December 31, 2017 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Hierarchy Level Publicly held debt $ 450,893 $ 453,147 $ 451,321 $ 462,604 2 Non-publicly held debt 589,357 526,887 719,681 660,065 3 Total long-term debt $ 1,040,250 $ 980,034 $ 1,171,002 $ 1,122,669

Stockholders' Equity Repurchase

Stockholders' Equity Repurchases (Tables)	6 Months Ended
	Jun. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Treasury Stock [Text Block]	Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Shares repurchased (not in thousands) (1) None 589,057 None 604,497 Average price per share NA $ 142.16 NA $ 142.66 Total (in thousands) None $ 83,740 None $ 86,240

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Computation of Net Income Per Share, Basic and Diluted	The following table sets forth the computation of net income per share, on a basic and diluted basis, for the periods indicated (share count and dollar amounts other than per-share amounts in table are in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Basic: Net income $ 50,016 $ 49,038 $ 105,209 $ 91,389 Less net income allocated to participating securities (659 ) (789 ) (1,427 ) (1,482 ) Net income attributable to common stock $ 49,357 $ 48,249 $ 103,782 $ 89,907 Earnings per share, basic $ 3.10 $ 2.98 $ 6.53 $ 5.52 Weighted-average shares outstanding 15,939 16,198 15,898 16,290 Diluted: Net income $ 50,016 $ 49,038 $ 105,209 $ 91,389 Less net income allocated to participating securities (658 ) (789 ) (1,425 ) (1,480 ) Net income attributable to common stock $ 49,358 $ 48,249 $ 103,784 $ 89,909 Earnings per share, diluted $ 3.10 $ 2.97 $ 6.52 $ 5.51 Weighted-average shares outstanding 15,939 16,198 15,898 16,290 Dilutive effect of stock options and restricted stock 44 71 63 92 Adjusted weighted-average shares outstanding under treasury stock method 15,983 16,269 15,961 16,382 Participating securities excluded under two-class method (38 ) (49 ) (47 ) (65 ) Adjusted weighted-average shares outstanding under two-class method 15,945 16,220 15,914 16,317

Commitments and Contingencies P

Commitments and Contingencies Payments Related to Commitments to Purchase (Tables)	6 Months Ended
	Jun. 30, 2018
Payments Related to Commitments to Purchase [Abstract]
Long-term Purchase Commitment [Table Text Block]	Future minimum fixed payments for the Company's commitments related to the acquisition of aircraft (including aircraft lease obligations), airport fees under use and lease agreements, and other operating lease obligations are as follows as of June 30, 2018 (in thousands): As of June 30, 2018 Remaining in 2018 $ 79,148 2019 123,164 2020 67,422 2021 26,288 2022 23,569 Thereafter 150,598 Total commitments $ 470,189

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue Recognition [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]	Certain prior period amounts have been recast to conform to the adoption of the New Revenue Standard as shown in the tables below. Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 (in thousands, except per share As Previously Reported Current Presentation As Previously Reported Current Presentation data) Adjustments Adjustments Income Statement: Passenger revenue (1) $ 220,615 $ 146,635 $ 367,250 $ 432,713 $ 282,373 $ 715,086 Air-related charges 145,405 (145,405 ) — 276,970 (276,970 ) — Sales and marketing 12,861 631 13,492 22,859 3,963 26,822 Income tax provision 29,800 36 29,836 54,279 158 54,437 Net income 48,475 563 49,038 90,107 1,282 91,389 Diluted earnings per share $ 2.94 $ 0.03 $ 2.97 $ 5.43 $ 0.08 $ 5.51 (1) Passenger revenue previously reported as Scheduled service revenue. December 31, 2017 As Previously Current (in thousands) Reported Adjustments Presentation Balance Sheet: Air traffic liability $ 210,184 $ (5,885 ) $ 204,299 Deferred income taxes 118,492 521 119,013 Retained earnings 902,579 5,364 907,943
Disaggregation of Revenue [Table Text Block]	Passenger revenue is primarily composed of passenger ticket sales, credit voucher breakage, seat fees, baggage fees, and other travel-related services performed in conjunction with a passenger’s flight, as well as co-brand point redemptions as outlined below: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2018 2017 2018 2017 Scheduled service $ 235,746 $ 220,811 $ 474,267 $ 435,075 Air-related ancillary charges 167,630 145,887 322,347 279,111 Co-brand redemptions 2,196 552 5,729 900 Total passenger revenue $ 405,572 $ 367,250 $ 802,343 $ 715,086
Contract with Customer, Asset and Liability [Table Text Block]	The following table presents the activity of the current and non-current point liabilities (in thousands): 2018 Balance at January 1 $ 8,903 Points awarded 6,898 Points redeemed (5,730 ) Balance at June 30 $ 10,071

Summary of Significant Accoun27

Summary of Significant Accounting Policies Policies (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017
Adjustments for New Accounting Pronouncements [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 600
Passenger revenue	$ 405,572	$ 367,250	$ 802,343	$ 715,086
Air-related charges		0		0
Sales and marketing	18,348	13,492	37,426	26,822
Income Tax Expense (Benefit)	13,027	29,836	27,225	54,437
Net income	$ 50,016	$ 49,038	$ 105,209	$ 91,389
Diluted earnings per share	$ 3.10	$ 2.97	$ 6.52	$ 5.51
Air traffic liability	$ (236,932)		$ (236,932)			$ (204,299)
Deferred income taxes	144,254		144,254			119,013
Retained earnings	$ 991,109		$ 991,109			907,943
Calculated under Revenue Guidance in Effect before Topic 606
Adjustments for New Accounting Pronouncements [Line Items]
Passenger revenue		$ 220,615		$ 432,713
Air-related charges		145,405		276,970
Sales and marketing		12,861		22,859
Income Tax Expense (Benefit)		29,800		54,279
Net income		$ 48,475		$ 90,107
Diluted earnings per share		$ 2.94		$ 5.43
Air traffic liability						(210,184)
Deferred income taxes						118,492
Retained earnings						902,579
Difference between Revenue Guidance in Effect before and after Topic 606
Adjustments for New Accounting Pronouncements [Line Items]
Passenger revenue		$ 146,635		$ 282,373
Air-related charges		(145,405)		(276,970)
Sales and marketing		631		3,963
Income Tax Expense (Benefit)		36		158
Net income		$ 563		$ 1,282
Diluted earnings per share		$ 0.03		$ 0.08
Air traffic liability						5,885
Deferred income taxes						521
Retained earnings						$ 5,364

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Flight equipment, including pre-delivery deposits	$ 1,785,184	$ 1,539,433
Computer Hardware and Software	131,661	123,675
Other Property and Equipment	151,802	125,855
Total property and equipment	2,068,647	1,788,963
Less accumulated depreciation and amortization	321,940	276,548
Property and equipment, net	$ 1,746,707	$ 1,512,415

Long-Term Debt Long-Term Debt -

Long-Term Debt Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes Payable	$ 1,040,250	$ 1,171,002
Secured Long-term Debt, Noncurrent	1,136,714	1,164,892
Less current maturities	144,392	214,761
Long-term debt and capital leases, net of current maturities and related costs	992,322	950,131
Fixed-rate debt and capital lease obligations due through 2030
Debt Instrument [Line Items]
Notes Payable	577,452	465,462
Variable-rate debt due through 2027
Debt Instrument [Line Items]
Notes Payable	$ 559,262	$ 699,430
Weighted average fixed-interest rate on debt
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate, at Point in Time	5.40%	5.40%
Weighted average variable-interest rate on debt
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate, at Point in Time	4.00%	3.30%

Long-Term Debt (Detail)

Long-Term Debt (Detail) - USD ($) $ in Thousands	1 Months Ended
	Dec. 31, 2016	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 01, 2016	Dec. 31, 2015	Jun. 01, 2014
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year		$ 92,500
Long-term Debt, Maturities, Repayments of Principal in Year Two		555,400
Long-term Debt, Maturities, Repayments of Principal in Year Three		103,500
Long-term Debt, Maturities, Repayments of Principal in Year Four		76,600
Long-term Debt, Maturities, Repayments of Principal in Year Five		49,200
Long-term Debt, Maturities, Repayments of Principal after Year Five		259,500
Debt Instrument, Face Amount		10,800
Secured Long-term Debt, Noncurrent		$ 1,136,714		$ 1,164,892
Line of Credit Facility, Maximum Borrowing Capacity			$ 81,000			$ 56,000
Unsecured Long-term Debt, Noncurrent					$ 150,000		$ 300,000
Debt Instrument, Redemption Price, Percentage	101.50%
Secured Debt
Debt Instrument, Interest Rate, Stated Percentage		4.15%
Unsecured Debt
Debt Instrument, Interest Rate, Stated Percentage		5.50%

Long-Term Debt Schedule of Ma31

Long-Term Debt Schedule of Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 81,000		$ 56,000
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 92,500
Long-term Debt, Maturities, Repayments of Principal in Year Two	555,400
Long-term Debt, Maturities, Repayments of Principal in Year Three	103,500
Long-term Debt, Maturities, Repayments of Principal in Year Four	76,600
Long-term Debt, Maturities, Repayments of Principal in Year Five	49,200
Long-term Debt, Maturities, Repayments of Principal after Year Five	259,500
Long-term Debt, Fair Value	$ 1,136,714		$ 1,164,892

Fair Value Measurements (Detail

Fair Value Measurements (Detail) - Fair Value Measurements at Reporting Date Using - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Measurements, Recurring
Available-for-sale Securities	$ 414,951	$ 463,522
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Available-for-sale Securities	115	1,297
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Available-for-sale Securities	414,836	462,225
Short-term Investments | Fair Value, Measurements, Recurring
Available-for-sale Securities	343,180	352,681
Short-term Investments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Available-for-sale Securities	343,180	352,681
Short-term Investments | Fair Value, Measurements, Recurring | Commercial paper
Available-for-sale Securities	141,091	108,678
Short-term Investments | Fair Value, Measurements, Recurring | Commercial paper | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | Commercial paper | Fair Value, Inputs, Level 2
Available-for-sale Securities	141,091	108,678
Short-term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities
Available-for-sale Securities	30,718	31,428
Short-term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	30,718	31,428
Short-term Investments | Fair Value, Measurements, Recurring | Municipal debt securities
Available-for-sale Securities	53,143	101,290
Short-term Investments | Fair Value, Measurements, Recurring | Municipal debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | Municipal debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	53,143	101,290
Short-term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Available-for-sale Securities	116,804	107,878
Short-term Investments | Fair Value, Measurements, Recurring | Corporate debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | Corporate debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	116,804	107,878
Short-term Investments | Fair Value, Measurements, Recurring | US Treasury Securities
Available-for-sale Securities	1,424	3,407
Short-term Investments | Fair Value, Measurements, Recurring | US Treasury Securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Short-term Investments | Fair Value, Measurements, Recurring | US Treasury Securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	1,424	3,407
Long Term Investments | Municipal debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Municipal debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	0	9,405
Long Term Investments | Fair Value, Measurements, Recurring
Available-for-sale Securities	56,379	78,852
Long Term Investments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Available-for-sale Securities	56,379	78,852
Long Term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities
Available-for-sale Securities	10,022	5,775
Long Term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Fair Value, Measurements, Recurring | Federal agency debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	10,022	5,775
Long Term Investments | Fair Value, Measurements, Recurring | Municipal debt securities
Available-for-sale Securities	0	9,405
Long Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Available-for-sale Securities	43,363	60,396
Long Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	43,363	60,396
Long Term Investments | Fair Value, Measurements, Recurring | US Treasury Securities
Available-for-sale Securities	2,973	2,994
Long Term Investments | Fair Value, Measurements, Recurring | US Treasury Securities | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Fair Value, Measurements, Recurring | US Treasury Securities | Fair Value, Inputs, Level 2
Available-for-sale Securities	2,973	2,994
Long Term Investments | Fair Value, Measurements, Recurring | Derivative Financial Instruments, Assets
Available-for-sale Securities	21	282
Long Term Investments | Fair Value, Measurements, Recurring | Derivative Financial Instruments, Assets | Fair Value, Inputs, Level 1
Available-for-sale Securities	0	0
Long Term Investments | Fair Value, Measurements, Recurring | Derivative Financial Instruments, Assets | Fair Value, Inputs, Level 2
Available-for-sale Securities	21	282
Cash Equivalents | Fair Value, Measurements, Recurring
Cash Equivalents	15,392	31,989
Cash Equivalents | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Cash Equivalents	115	1,297
Cash Equivalents | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Cash Equivalents	15,277	30,692
Cash Equivalents | Fair Value, Measurements, Recurring | US Treasury Bonds
Cash Equivalents	115	1,297
Cash Equivalents | Fair Value, Measurements, Recurring | US Treasury Bonds | Fair Value, Inputs, Level 1
Cash Equivalents	115	1,297
Cash Equivalents | Fair Value, Measurements, Recurring | US Treasury Bonds | Fair Value, Inputs, Level 2
Cash Equivalents	0	0
Cash Equivalents | Fair Value, Measurements, Recurring | Commercial paper
Cash Equivalents	9,952	27,910
Cash Equivalents | Fair Value, Measurements, Recurring | Commercial paper | Fair Value, Inputs, Level 1
Cash Equivalents	0	0
Cash Equivalents | Fair Value, Measurements, Recurring | Commercial paper | Fair Value, Inputs, Level 2
Cash Equivalents	9,952	27,910
Cash Equivalents | Fair Value, Measurements, Recurring | Municipal debt securities
Cash Equivalents	5,325	2,782
Cash Equivalents | Fair Value, Measurements, Recurring | Municipal debt securities | Fair Value, Inputs, Level 1
Cash Equivalents	0	0
Cash Equivalents | Fair Value, Measurements, Recurring | Municipal debt securities | Fair Value, Inputs, Level 2
Cash Equivalents	$ 5,325	$ 2,782

Fair Value Measurements Estimat

Fair Value Measurements Estimated Fair Value of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	$ 1,136,714	$ 1,164,892
Notes Payable	1,040,250	1,171,002
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	980,034	1,122,669
Publicly Held Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	450,893	451,321
Publicly Held Debt | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	453,147	462,604
Non-Publicly Held Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	589,357	719,681
Non-Publicly Held Debt | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Secured Long-term Debt, Noncurrent	$ 526,887	$ 660,065

Stockholders' Equity (Detail)

Stockholders' Equity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Dividends Payable, Amount Per Share	$ 1.40		$ 1.40
Stock Repurchased During Period, Shares	0	589,057	0	604,497
Treasury Stock Acquired, Average Cost Per Share		$ 142.16		$ 142.66
Stock Repurchased During Period, Value	$ 0	$ 83,740	$ 0	$ 86,240
Payments of Dividends			$ 22,605	$ 23,204

Earnings per Share (Detail) - E

Earnings per Share (Detail) - Earnings Per Share - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,379		607
Basic:
Net income attributable to Allegiant Travel Company (in Dollars)	$ 50,016	$ 49,038	$ 105,209	$ 91,389
Less: Net income allocated to participating securities (in Dollars)	(659)	(789)	(1,427)	(1,482)
Net income attributable to common stock (in Dollars)	$ 49,357	$ 48,249	$ 103,782	$ 89,907
Net income per share, basic (in Dollars per share)	$ 3.10	$ 2.98	$ 6.53	$ 5.52
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	$ (658)	$ (789)	$ (1,425)	$ (1,480)
Net Income (Loss) Available to Common Stockholders, Diluted	$ 49,358	$ 48,249	$ 103,784	$ 89,909
Diluted earnings per share	$ 3.10	$ 2.97	$ 6.52	$ 5.51
Weighted-average shares outstanding	15,939,000	16,198,000	15,898,000	16,290,000
Dilutive effect of stock options, restricted stock and stock-settled stock appreciation rights	44,000	71,000	63,000	92,000
Adjusted weighted-average shares outstanding under treasury stock method	15,983,000	16,269,000	15,961,000	16,382,000
Participating securities excluded under two-class method	(38,000)	(49,000)	(47,000)	(65,000)
Two-Class Method, Weighted Average Number of Shares Outstanding, Diluted	15,945,000	16,220,000	15,914,000	16,317,000

Commitments and Contingencies (

Commitments and Contingencies (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)aircraft
Long-term Purchase Commitment [Line Items]
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year	$ 79,148
Unrecorded Unconditional Purchase Obligation, Due within Two Years	123,164
Unrecorded Unconditional Purchase Obligation, Due within Three Years	67,422
Unrecorded Unconditional Purchase Obligation, Due within Four Years	26,288
Unrecorded Unconditional Purchase Obligation, Due within Five Years	23,569
Unrecorded Unconditional Purchase Obligation, Due after Five Years	$ 150,598
Number Of Aircraft Committed To Purchase | aircraft	11
Unrecorded Unconditional Purchase Obligation	$ 470,189
Airbus A320 Aircraft Series
Long-term Purchase Commitment [Line Items]
Number of Aircraft Committed to be Leased | aircraft	13
Aircraft scheduled to be acquired | aircraft	9
In service | Airbus A320 Aircraft Series
Long-term Purchase Commitment [Line Items]
Aircraft acquired | aircraft	3
Not in service | Airbus A320 Aircraft Series
Long-term Purchase Commitment [Line Items]
Aircraft acquired | aircraft	1

Commitments and Contingencies37

Commitments and Contingencies Payments Related to Commitments to Purchase (Details) $ in Thousands	Jun. 30, 2018USD ($)
Payments Related to Commitments to Purchase [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year	$ 79,148
Unrecorded Unconditional Purchase Obligation, Due within Two Years	123,164
Unrecorded Unconditional Purchase Obligation, Due within Three Years	67,422
Unrecorded Unconditional Purchase Obligation, Due within Four Years	26,288
Unrecorded Unconditional Purchase Obligation, Due within Five Years	23,569
Unrecorded Unconditional Purchase Obligation, Due after Five Years	150,598
Unrecorded Unconditional Purchase Obligation	$ 470,189

Related Party (Details)

Related Party (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 0.2

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Passenger revenue	$ 405,572	$ 367,250	$ 802,343	$ 715,086
Air-related charges		0		0
Scheduled Service Revenue
Disaggregation of Revenue [Line Items]
Passenger revenue	235,746	220,811	474,267	435,075
Co-brand Revenue
Disaggregation of Revenue [Line Items]
Passenger revenue	2,196	552	5,729	900
Air-related revenue
Disaggregation of Revenue [Line Items]
Passenger revenue	$ 167,630	145,887	$ 322,347	279,111
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Passenger revenue		220,615		432,713
Air-related charges		$ 145,405		$ 276,970

Revenue Recognition Points Liab

Revenue Recognition Points Liability (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Points Liability [Abstract]
Points Liability Start of Period	$ 8,903
Points redeemed	(5,730)
Points awarded	6,898
Points Liability End of Period	$ 10,071

Revenue Recognition Passenger R

Revenue Recognition Passenger Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Revenue Recognition [Abstract]
Increase (Decrease) in Deferred Air Traffic Revenue	$ 187,800
Air traffic liability	$ 236,932	$ 204,299

Revenue Recognition Disaggregat

Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Adjustments for New Accounting Pronouncements [Line Items]
Air Traffic Liability, Current	$ 236,932		$ 236,932		$ 204,299
Deferred Tax Liabilities, Net, Noncurrent	144,254		144,254		119,013
Retained Earnings (Accumulated Deficit)	991,109		991,109		907,943
Passenger Revenue	405,572	$ 367,250	802,343	$ 715,086
Air-related charges		0		0
Selling and Marketing Expense	18,348	13,492	37,426	26,822
Income Tax Expense (Benefit)	13,027	29,836	27,225	54,437
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 50,016	$ 49,038	$ 105,209	$ 91,389
Earnings Per Share, Diluted	$ 3.10	$ 2.97	$ 6.52	$ 5.51
Calculated under Revenue Guidance in Effect before Topic 606
Adjustments for New Accounting Pronouncements [Line Items]
Air Traffic Liability, Current					210,184
Deferred Tax Liabilities, Net, Noncurrent					118,492
Retained Earnings (Accumulated Deficit)					902,579
Passenger Revenue		$ 220,615		$ 432,713
Air-related charges		145,405		276,970
Selling and Marketing Expense		12,861		22,859
Income Tax Expense (Benefit)		29,800		54,279
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 48,475		$ 90,107
Earnings Per Share, Diluted		$ 2.94		$ 5.43
Difference between Revenue Guidance in Effect before and after Topic 606
Adjustments for New Accounting Pronouncements [Line Items]
Air Traffic Liability, Current					(5,885)
Deferred Tax Liabilities, Net, Noncurrent					521
Retained Earnings (Accumulated Deficit)					$ 5,364
Passenger Revenue		$ 146,635		$ 282,373
Air-related charges		(145,405)		(276,970)
Selling and Marketing Expense		631		3,963
Income Tax Expense (Benefit)		36		158
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 563		$ 1,282
Earnings Per Share, Diluted		$ 0.03		$ 0.08

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands	Jul. 01, 2018	Jun. 30, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Secured Long-term Debt, Noncurrent		$ 1,136,714	$ 1,164,892
Subsequent Event
Subsequent Event [Line Items]
Secured Long-term Debt, Noncurrent	$ 34,500
Proceeds from Lines of Credit	$ 46,900
Airbus A320 Aircraft Series | Subsequent Event
Subsequent Event [Line Items]
Debt Instrument, Collateral	1