Spirit Airlines (SAVEQ) 10-Q 30 Oct 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 18, 2013
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Entity Registrant Name	SPIRIT AIRLINES, INC.
Entity Central Index Key	1498710
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		72,647,167

Condensed_Statements_Of_Operat

Condensed Statements Of Operations (unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating revenues:
Passenger	$279,499	$202,181	$739,515	$594,071
Non-ticket	177,126	140,136	494,886	396,049
Total operating revenues	456,625	342,317	1,234,401	990,120
Operating expenses:
Aircraft fuel	144,986	122,016	411,903	350,974
Salaries, wages and benefits	66,805	54,413	192,758	160,556
Aircraft rent	42,134	37,536	125,121	106,469
Landing fees and other rents	22,106	19,060	61,508	51,240
Distribution	17,916	14,620	50,874	43,559
Maintenance, materials and repairs	16,908	14,211	43,890	37,254
Depreciation and amortization	8,475	3,815	22,403	10,012
Other operating	38,884	35,253	110,799	95,862
Loss on disposal of assets	165	0	426	482
Special charges (credits)	442	-8,288	488	-8,345
Total operating expenses	358,821	292,636	1,020,170	848,063
Operating income	97,804	49,681	214,231	142,057
Other (income) expense:
Interest expense	36	10	140	1,334
Capitalized interest	-36	-10	-140	-1,334
Interest income	-87	-171	-308	-766
Other expense	115	109	252	236
Total other (income) expense	28	-62	-56	-530
Income before income taxes	97,776	49,743	214,287	142,587
Provision for income taxes	36,673	18,859	80,562	53,693
Net income	$61,103	$30,884	$133,725	$88,894
Basic earnings per share	$0.84	$0.43	$1.84	$1.23
Diluted earnings per share	$0.84	$0.43	$1.83	$1.22

Condensed_Balance_Sheets_unaud

Condensed Balance Sheets (unaudited) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$540,195	$416,816
Accounts receivable, net	27,838	22,740
Deferred income taxes	14,512	12,591
Other current assets	79,299	95,210
Total current assets	661,844	547,357
Property and equipment:
Flight equipment	5,148	2,648
Ground and other equipment	49,567	43,580
Less accumulated depreciation	-23,202	-17,825
Total property and equipment	31,513	28,403
Deposits on flight equipment purchase contracts	132,483	96,692
Aircraft maintenance deposits	145,598	122,379
Deferred heavy maintenance	110,514	80,533
Other long-term assets	43,187	44,520
Total assets	1,125,139	919,884
Current liabilities:
Accounts payable	20,766	24,166
Air traffic liability	180,735	131,414
Other current liabilities	129,770	121,314
Total current liabilities	331,271	276,894
Long-term deferred income taxes	43,932	33,216
Deferred credits and other long-term liabilities	26,167	27,239
Shareholders’ equity:
Common stock	7	7
Additional paid-in-capital	513,142	504,527
Treasury stock	-2,257	-1,151
Retained earnings	212,877	79,152
Total shareholders’ equity	723,769	582,535
Total liabilities and shareholders’ equity	$1,125,139	$919,884

Condensed_Statements_Of_Cash_F

Condensed Statements Of Cash Flows (unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Statement of Cash Flows [Abstract]
Net cash provided by operating activities	$173,631	$88,807
Investing activities:
Proceeds from sale of property and equipment	0	14
Proceeds from sale of slots	0	9,060
Pre-delivery deposits for flight equipment, net of refunds	-41,328	-6,817
Purchase of property and equipment	-17,028	-21,711
Net cash used in investing activities	-58,356	-19,454
Financing activities:
Proceeds from options exercised	675	410
Proceeds from sale and leaseback transactions	6,900	12,427
Payments to pre-IPO shareholders pursuant to tax receivable agreement	0	-26,905
Excess tax benefits from share-based compensation	1,635	1,466
Repurchase of common stock	-1,106	-936
Net cash provided by (used in) financing activities	8,104	-13,538
Net increase in cash and cash equivalents	123,379	55,815
Cash and cash equivalents at beginning of period	416,816	343,328
Cash and cash equivalents at end of period	540,195	399,143
Cash payments for:
Interest	26	297
Taxes	$60,942	$39,350

Basis_Of_Presentation

Basis Of Presentation	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis Of Presentation	Basis of Presentation
	The accompanying unaudited condensed financial statements include the accounts of Spirit Airlines, Inc. (the Company). These unaudited condensed 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 information and footnote disclosures normally included in the annual financial statements prepared in accordance with U.S. generally accepted accounting principles (GAAP) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission for Form 10-Q. These unaudited interim condensed financial statements should be read in conjunction with the audited financial statements of the Company and notes thereto included in the Annual Report on Form 10-K for the year ended December 31, 2012 filed with the Securities and Exchange Commission.
	The preparation of financial statements in conformity with 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 could differ from these estimates.
	The interim results reflected in the unaudited condensed financial statements are not necessarily indicative of the results that may be expected for other interim periods or for the full year.
	Certain prior period amounts have been reclassified to conform to the current year's presentation.

Recent_Accounting_Developments

Recent Accounting Developments	9 Months Ended
	Sep. 30, 2013
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Developments	Recent Accounting Developments
	In December 2011, the FASB issued amendments to Accounting Standards Update No. 2011-11, Balance Sheet (Topic 210); Disclosures about Offsetting Assets and Liabilities (ASU 2011-11). The amendments in this update are designed to enhance disclosures by requiring improved information about financial instruments and derivative instruments that are either (a) offset in accordance with certain right to set-off conditions prescribed by current accounting guidance or (b) subject to an enforceable master netting arrangement or similar agreement, irrespective of whether they are offset in accordance with current accounting guidance. On January 1, 2013, the Company adopted ASU 2011-11.
	In January 2013, the FASB issued Accounting Standards Update No. 2013-01, Scope Clarification of Disclosures about Offsetting Assets and Liabilities (ASU 2013-01), to limit the scope of ASU 2011-11 and its new balance sheet offsetting disclosure requirements to derivatives (including bifurcated embedded derivatives), repurchase agreements and reverse repurchase agreements, and securities borrowing and lending transactions. On January 1, 2013, the Company adopted ASU 2013-01 in conjunction with ASU 2011-11.

Special_Charges_and_Credits

Special Charges and Credits	9 Months Ended
	Sep. 30, 2013
Restructuring and Related Activities [Abstract]
Special Charges and Credits	Special Charges and Credits
	Secondary Offering Costs
	Special charges and credits for the nine months ended September 30, 2013 primarily include costs related to an underwritten public offering of 12,070,920 shares of common stock by certain stockholders affiliated with Indigo Partners LLC (Indigo) completed during the third quarter of 2013. The Company incurred a total of $0.4 million in costs related to this offering. The Company did not receive any proceeds from this offering.
	On January 25, 2012, certain stockholders of the Company, including affiliates of Oaktree Capital Management and Indigo and certain members of the Company's executive team, sold an aggregate of 12,650,000 shares of common stock in an underwritten public offering. The Company incurred a total of $1.3 million in costs between 2011 and 2012 related to this offering, of which $0.5 million were incurred during the nine months ended September 30, 2012. These costs were offset by reimbursements from certain selling shareholders of $0.6 million in accordance with the Fourth Amendment to the Second Amended and Restated Investor Rights Agreement. The Company did not receive any proceeds from this offering.

Earnings_per_Share

Earnings per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings per Share
		Earnings per Share
	The following table sets forth the computation of basic and diluted earnings per common share:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2013		2012		2013		2012
		(in thousands, except per share amounts)
	Numerator
	Net income	$	61,103	$	30,884	$	133,725	$	88,894
	Denominator
	Weighted-average shares outstanding, basic	72,632		72,427		72,571		72,367
	Effect of dilutive stock awards	371		231		363		214
	Adjusted weighted-average shares outstanding, diluted	73,003		72,658		72,934		72,581
	Net Income per Share
	Basic earnings per common share	$	0.84	$	0.43	$	1.84	$	1.23
	Diluted earnings per common share	$	0.84	$	0.43	$	1.83	$	1.22
	Potentially dilutive amounts excluded from calculations:
	Stock options and restricted stock units	1		—		1		—

Accrued_Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2013
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities
	Other current liabilities as of September 30, 2013 and December 31, 2012 consist of the following:
		September 30, 2013		December 31, 2012
		(in thousands)
	Federal excise and other passenger taxes and fees payable	$	24,051	$	23,401
	Aircraft maintenance	23,784		22,319
	Salaries and wages	22,357		21,057
	Airport expenses	16,757		16,024
	Fuel	12,994		11,219
	Aircraft and facility rent	6,133		8,020
	Tax receivable agreement	5,643		7,987
	Other	18,051		11,287
	Accrued liabilities	$	129,770	$	121,314

Financial_Instruments_and_Risk

Financial Instruments and Risk Management	9 Months Ended
	Sep. 30, 2013
Investments, All Other Investments [Abstract]
Financial Instruments and Risk Management	Financial Instruments and Risk Management
	As part of the Company’s risk management program, the Company from time to time uses a variety of financial instruments to reduce its exposure to fluctuations in the price of jet fuel. The Company does not hold or issue derivative financial instruments for trading purposes.
	The Company is exposed to credit losses in the event of nonperformance by counterparties to these financial instruments. The Company periodically reviews and seeks to mitigate exposure to the financial deterioration and nonperformance of any counterparty by monitoring the absolute exposure levels, each counterparty's credit ratings, and the historical performance of the counterparties relating to hedge transactions. The credit exposure related to these financial instruments is limited to the fair value of contracts in a net receivable position at the reporting date. The Company also maintains security agreements that require the Company to post collateral if the value of selected instruments falls below specified mark-to-market thresholds. As of September 30, 2013, the Company was not required to post collateral for these instruments.
	The Company records financial derivative instruments at fair value, which includes an evaluation of each counterparty's credit risk. The Company's derivative contracts generally consist of United States Gulf Coast jet fuel swaps (jet fuel swaps) and United States Gulf Coast jet fuel options (jet fuel options). Jet fuel swaps are agreements to protect the refining price risk between the price of crude oil and the price of refined jet fuel. Jet fuel options are costless collar contracts to manage the risk of increasing fuel prices. Fair value of the instruments is determined using standard option valuation models.
	The Company chose not to elect hedge accounting on any derivative instruments entered into during the three and nine months ended September 30, 2013 and 2012 and, as a result, changes in the fair value of these fuel hedge contracts are recorded each period in aircraft fuel expense.
	The following table summarizes the components of aircraft fuel expense for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013		2012
		(in thousands)
	Into-plane fuel cost	$	143,978		$	123,517		$	402,066	$	351,057
	Settlement losses (gains)	6,663			(580		)	6,348		(543		)
	Unrealized mark-to-market losses (gains)	(5,655		)	(921		)	3,489		460
	Aircraft fuel	$	144,986		$	122,016		$	411,903	$	350,974
	All realized gains and losses are reflected in the accompanying statements of cash flows in cash flow from operating activities.
	During peak hurricane season (August through October), the Company enters into jet fuel swap agreements to protect the refining price risk between the price of crude oil and the price of refined jet fuel. As of September 30, 2013 and December 31, 2012, the Company had fuel hedges consisting of jet fuel swaps and jet fuel options, respectively, with crude oil and refined products as the underlying commodities. As of September 30, 2013, the Company had approximately 21% of its forecast fourth quarter 2013 fuel consumption protected from refining risk using jet fuel swaps. As of December 31, 2012, the Company had jet fuel option agreements in place to protect 7.8 million gallons, or approximately 5%, of its 2013 anticipated jet fuel consumption at a weighted-average ceiling and floor price of $3.09 and $2.84 per gallon, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Aircraft-Related Commitments and Financing Arrangements
	The Company’s contractual purchase commitments consist primarily of aircraft and engine acquisitions through manufacturers and aircraft leasing companies. On June 20, 2013, the Company entered into an amendment to the Airbus A320 Family Purchase Agreement, by and between the Company and Airbus S.A.S., dated May 5, 2004 (Airbus Amendment) for the order of an additional 20 Airbus A321 aircraft. These aircraft are in addition to the 95 aircraft not yet delivered under Spirit's existing order with Airbus and are scheduled for delivery between 2015 and 2017. On October 1, 2013, the Company entered into agreements with International Aero Engines AG (IAE) and Pratt & Whitney (collectively, the IAE & P&W Agreement) for the provision and servicing of engines to power its fleet of Airbus A320-family aircraft. The commitments reflected below are inclusive of the additional commitments resulting from the IAE & P&W Agreement. The Company's aircraft orders, including the conversion of 10 Airbus A320 orders to Airbus A321 orders and the conversion of 5 Airbus A321 orders to Airbus A321neo orders, consisted of 115 A320 family aircraft (40 of the existing A320 model, 45 A320neos, 25 of the existing A321 model, and 5 A321neos) with Airbus, 5 direct operating leases for A320neos with a third party, 6 spare engine orders for V2500 SelectOne™ engines with IAE and 9 spare engine orders for PurePower PW1100G-JM engines with Pratt & Whitney. Aircraft are scheduled for delivery from 2013 through 2021, and spare engines are scheduled for delivery from 2014 through 2023. Committed expenditures for these aircraft and related flight equipment, including estimated amounts for contractual price escalations and pre-delivery payments, will be approximately $136 million for the remainder of 2013, $412 million in 2014, $794 million in 2015, $640 million in 2016, $816 million in 2017, and $2,743 million in 2018 and beyond. We have secured financing commitments with third parties for our next ten aircraft deliveries from Airbus, which are scheduled for delivery between 2013 and 2014. We do not have financing commitments in place for the remaining 105 Airbus firm aircraft orders scheduled for delivery between 2015 and 2021.
	During the first nine months of 2013, the Company took delivery of six aircraft, two of which were financed via direct operating leases and the remaining four under sale and leaseback transactions with third-party aircraft lessors. The four sale and leaseback transactions resulted in net deferred losses of $1.4 million. Deferred losses are included in other long-term assets on the accompanying balance sheet. Deferred losses are recognized as an increase to rent expense on a straight-line basis over the term of the respective operating leases. Deferred gains are included in deferred credits and other long-term liabilities on the accompanying balance sheet. Deferred gains are recognized as a decrease to rent expense on a straight-line basis over the term of the respective operating leases. The Company had agreements in place prior to the delivery of these aircraft which resulted in the settlement of the purchase obligation by the lessor and the refund of $21.5 million in pre-delivery deposits from Airbus during the nine months ended September 30, 2013. The refunded pre-delivery deposits have been disclosed in the accompanying statements of cash flows as investing activities within pre-delivery deposits for flight equipment, net of refunds. In addition, the Company entered into a sale and leaseback transaction with third-party lessors for the sale and leaseback of one V2500 SelectOne™ IAE engine. Cash outflows related to the purchase of the engine have been disclosed in the accompanying statements of cash flows as investing activities within purchases of property and equipment and the cash inflows from the sale of the engine as financing activities within proceeds received from sale and leaseback transactions. All of the leases from these sale and leaseback transactions are accounted for as operating leases. Under the terms of the lease agreements, the Company will continue to operate and maintain the aircraft. Payments under the lease agreements are fixed for the term of the lease. The lease agreements contain standard termination events, including termination upon a breach of the Company's obligations to make rental payments and upon any other material breach of the Company's obligations under the leases, and standard maintenance and return condition provisions. These return provisions are evaluated at inception of the lease and throughout the lease terms and are accounted for as additional rent expense when it is probable that such amounts will be paid to the lessor. Upon a termination of the lease due to a breach by the Company, the Company would be liable for standard contractual damages, possibly including damages suffered by the lessor in connection with remarketing the aircraft or while the aircraft is not leased to another party.
	Future minimum lease payments under noncancelable operating leases as of September 30, 2013 and the periods in which payments are due were as follows:
		Operating Lease Obligations
		(in thousands)
	Remainder of 2013	$	47,411
	2014	188,817
	2015	188,492
	2016	181,369
	2017	157,756
	2018 and thereafter	574,141
	Total minimum lease payments	$	1,337,986
	During the second quarter, the Company extended the operating leases on 14 of its Airbus A319 aircraft, which were previously set to expire in 2017 through 2019. These extensions resulted in an additional $72.8 million of lease commitments from 2017 through 2022.
	Some of the Company’s master lease agreements provide that the Company pays maintenance reserves to aircraft lessors to be held as collateral in advance of the Company’s required performance of major maintenance activities. Maintenance reserve payments are either fixed contractual amounts or utilization based. Fixed maintenance reserve payments for these aircraft and related flight equipment, including estimated amounts for contractual price escalations, are expected to be approximately $1.8 million for the remainder of 2013, $7.4 million in 2014, $7.6 million in 2015, $8.0 million in 2016, $7.4 million in 2017, and $24.2 million in 2018 and beyond. These lease agreements provide that maintenance reserves are reimbursable to the Company upon completion of the maintenance event in an amount equal to the lesser of (1) the amount of the maintenance reserve held by the lessor associated with the specific maintenance event or (2) the qualifying costs related to the specific maintenance event.
	Reservation System
	The Company is contractually obligated to pay the following minimum guaranteed payments to the provider of its reservation system as of September 30, 2013: $0.9 million for the remainder of 2013, $3.9 million in 2014, $3.9 million in 2015, $3.9 million in 2016, $3.9 million in 2017, and $2.6 million in 2018 and thereafter.
	Litigation
	The Company is subject to commercial litigation claims and to administrative and regulatory proceedings and reviews that may be asserted or maintained from time to time. The Company believes the ultimate outcome of such lawsuits, proceedings and reviews will not, individually or in the aggregate, have a material adverse effect on its financial position, liquidity or results of operations.
	Credit Card Processing Arrangements
	The Company has agreements with organizations that process credit card transactions arising from the purchase of air travel, baggage charges, and other ancillary services by customers. As it is standard in the airline industry, the Company's contractual arrangements with credit card processors permit them, under certain circumstances, to retain a holdback or other collateral, which the Company records as restricted cash, when future air travel and other future services are purchased via credit card transactions. The required holdback is the percentage of the Company's overall credit card sales that its credit card processors hold to cover refunds to customers if the Company fails to fulfill its flight obligations. If the Company fails to satisfy certain liquidity and other financial covenants, the processing agreements provide the processors the right to require the Company to maintain cash collateral up to approximately 100% of the Company's air traffic liability, resulting in a commensurate reduction of unrestricted cash. As of September 30, 2013 and December 31, 2012, the Company continued to be in compliance with its credit card processing agreements, and the processors were holding back $0 of remittances.
	The maximum potential exposure to cash holdbacks by the Company's credit card processors, based upon advance ticket sales and $9 Fare Club memberships as of September 30, 2013 and December 31, 2012, was $203.8 million and $144.8 million, respectively.
	Employees
	Approximately 59% of the Company’s employees are covered under collective bargaining agreements. The table below sets forth our employee groups and status of the collective bargaining agreements as of September 30, 2013.
	Employee Groups		Representative	Amendable Date	Percentage of Workforce
	Pilots		Air Line Pilots Association, International (ALPA)	August 2015	24%
	Flight Attendants		Association of Flight Attendants (AFA-CWA)	Aug-07	34%
	Dispatchers		Transport Workers Union (TWU)	Aug-18	1%
	During the third quarter of 2013, the Company reached a five-year agreement with the TWU. The Company is currently in negotiations with the AFA-CWA to reach a new collective bargaining agreement.
	The Company is self-insured for health care claims, up to a stop loss amount, for eligible participating employees and qualified dependent medical claims, subject to deductibles and limitations. The Company’s liabilities for claims incurred but not reported are determined based on an estimate of the ultimate aggregate liability for claims incurred. The estimate is calculated from actual claim rates and adjusted periodically as necessary. The Company has accrued $2.1 million and $1.9 million for health care claims as of September 30, 2013 and December 31, 2012, respectively.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Fair Value Measurements
		Fair Value Measurements
	Under ASC 820, Fair Value Measurements and Disclosures, disclosures are required about how fair value is determined for assets and liabilities, and a hierarchy for which these assets and liabilities must be grouped is established, based on significant levels of inputs, as follows:
	Level 1—Quoted prices in active markets for identical assets or liabilities.
	Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company utilizes several valuation techniques in order to assess the fair value of the Company’s financial assets and liabilities. The Company's derivative contracts generally consist of jet fuel swaps and jet fuel options. These instruments are valued using energy and commodity market data, which is derived by combining raw inputs with quantitative models and processes to generate forward curves and volatilities.
	The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
	Assets and liabilities measured at gross fair value on a recurring basis are summarized below:
		Fair Value Measurements as of September 30, 2013
		Total			Level		Level		Level
					1		2		3
		(in millions)
	Cash and cash equivalents	$	540.2		$	540.2	$	—	$	—
	Jet fuel swaps	1.7			—		1.7		—
	Total assets	$	541.9		$	540.2	$	1.7	$	—
	Jet fuel swaps	$	4.9		$	—	$	4.9	$	—
	Total liabilities	$	4.9		$	—	$	4.9	$	—
		Fair Value Measurements as of December 31, 2012
		Total			Level		Level		Level
					1		2		3
		(in millions)
	Cash and cash equivalents	$	416.8		$	416.8	$	—	$	—
	Jet fuel options	0.3			—		—		0.3
	Total assets	$	417.1		$	416.8	$	—	$	0.3
	Total liabilities	$	—		$	—	$	—	$	—
	Cash and cash equivalents at September 30, 2013 and December 31, 2012 are comprised of liquid money market funds and cash. The Company maintains cash with various high-quality financial institutions. The Company had no transfers of assets or liabilities between any of the above levels during the nine months ended September 30, 2013 and the year ended December 31, 2012.
	The Company did not elect hedge accounting on any of the derivative instruments, and as a result, changes in the fair values of these fuel hedge contracts are recorded each period in fuel expense. Fair values of the instruments are determined using standard option valuation models. The Company also considers counterparty risk and its own credit risk in its determination of all estimated fair values. Within the Condensed Balance Sheets, the Company offsets fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement. All derivative instruments are presented on a gross basis in the table above. The Company determines the fair value of jet fuel options utilizing an option pricing model based on inputs that are either readily available in public markets or can be derived from information available in publicly quoted markets. The Company has consistently applied these valuation techniques in all periods presented and believes it has obtained the most accurate information available for the types of derivative contracts it holds.
	The fair value of the Company's jet fuel swaps are 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 these instruments as Level 2. Due to the fact that certain inputs utilized to determine the fair value of the Company's jet fuel options are unobservable (principally implied volatility), the Company has categorized these instruments as Level 3.
	The Company's Valuation Group is made up of individuals from the Company's Risk Management, Treasury and Corporate Accounting departments. The Valuation Group is responsible for the Company's valuation policies, procedures and execution thereof. The Company's Valuation Group reports to the Company's Chief Financial Officer and Finance Committee, who approve all derivative transactions. The Valuation Group compares the results of the Company's internally developed valuation methods with counterparty reports at each balance sheet date and assesses the Company's valuation methods for accurateness and identifies any needs for modification.
	The following table presents the Company’s activity for assets and liabilities measured at gross fair value on a recurring basis using significant unobservable inputs (Level 3):
		Jet Fuel Option Activity for the Three Months Ended September 30, 2013
		(in millions)
	Balance at June 30, 2013	$	(0.3	)
	Total realized or unrealized gains (losses) included in earnings, net	0.5
	Settlements, net	(0.2		)
	Balance at September 30, 2013	$	—
		Jet Fuel Option Activity for the Nine Months Ended September 30, 2013
		(in millions)
	Balance at December 31, 2012	$	0.3
	Total realized or unrealized gains (losses) included in earnings, net	0.1
	Settlements, net	(0.4		)
	Balance at September 30, 2013	$	—
	The Company records the fair value adjustment of its aircraft fuel derivatives in the accompanying statement of operations within aircraft fuel and on the balance sheet within other current assets or other current liabilities, depending on whether the net fair value of the derivatives is in an asset or liability position as of the respective date.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation
	The Company has stock plans under which directors, officers, key employees, and consultants of the Company may be granted restricted stock awards, stock options and other equity-based instruments as a means of promoting the Company’s long-term growth and profitability. The plans are intended to encourage participants to contribute to and participate in the success of the Company.
	The Company's board of directors adopted, and the Company's stockholders approved, the Amended and Restated 2005 Incentive Stock Plan, or the 2005 Stock Plan, effective January 1, 2008. The total number of shares of common stock authorized for issue pursuant to awards granted under the 2005 Stock Plan was 2,500,000 shares. The 2005 Stock Plan provided for the grant of non-qualified stock options, stock appreciation rights, restricted stock, performance shares, phantom stock, restricted stock units and other awards that are valued in whole or in part by reference to the Company's stock.
	On May 9, 2011, the Company's board of directors adopted, and the Company's stockholders approved, the 2011 Equity Incentive Award Plan, or 2011 Plan. Under the 2011 Plan, 3,000,000 new shares of common stock are reserved for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights or SARs, restricted stock awards, restricted stock unit awards, deferred stock awards, dividend equivalent awards, stock payment awards, performance share awards and other stock-based awards, in addition to shares remaining available for future awards under our 2005 Stock Plan. The number of shares reserved for issuance or transfer pursuant to awards under the 2011 Plan will be increased by the number of shares represented by awards outstanding under the Company's 2005 Stock Plan that are forfeited or lapse unexercised. No further awards will be granted under the 2005 Stock Plan, and all outstanding awards will continue to be governed by their existing terms. As of September 30, 2013 and December 31, 2012, 2,709,523 and 2,689,490 shares of the Company’s common stock, respectively, remained available for future issuance under the 2011 Plan.
	Stock-based compensation cost is included within salaries, wages and benefits in operating expenses in the accompanying statements of operations. Stock-based compensation cost for the three and nine months ended September 30, 2013 and 2012, amounted to $1.2 million and $1.3 million, and $4.0 million and $3.0 million, respectively. The tax benefit recognized in income related to stock-based compensation for the three and nine months ended September 30, 2013 and 2012, was $0.4 million and $0.5 million, and $1.5 million and $1.1 million, respectively.
	Restricted Stock
	Restricted stock and restricted stock unit awards are valued at the fair value of the shares on the date of grant. Generally, granted shares and units vest 25% per year on each anniversary of issuance. Each restricted stock unit represents the right to receive one share of common stock upon vesting of such restricted stock unit. Compensation expense is recognized on a straight-line basis over the requisite service period.
	A summary of the status of the Company’s restricted stock shares (restricted stock awards and restricted stock unit awards) as of September 30, 2013 and changes during the nine months ended September 30, 2013 is presented below:
		Number of Shares			Weighted-Average
					Grant Date Fair Value ($)
	Outstanding at December 31, 2012	449,629			16.93
	Granted	135,005			25.9
	Vested	(165,745	)		13.15
	Forfeited	(89,744	)		19.09
	Outstanding at September 30, 2013	329,145			21.94
	There were 135,005 and 377,942 restricted stock shares granted during the nine months ended September 30, 2013 and 2012, respectively. The total fair value of restricted stock shares vested during the nine months ended September 30, 2013 and 2012 was $4.1 million and $3.6 million, respectively.
	As of September 30, 2013 and 2012, there was $6.1 million and $6.5 million, respectively, of total unrecognized compensation cost related to nonvested restricted stock to be recognized over a weighted-average period of 2.8 years and 3.4 years, respectively.
	Stock Options
	Stock option awards are granted with an exercise price equal to the fair market value of the Company’s common stock at the date of grant, vest over four years of continuous service, and have ten-year contractual terms. The fair value of each stock option award is estimated on the date of grant using the Black Scholes model. There were no options granted during the nine months ended September 30, 2013 or 2012. Expected volatilities are based on the historical volatility of a group of peer entities within the same industry. The expected term of options is based upon the simplified method, which represents the average of the vesting term and the contractual term. The risk-free interest rate is based on U.S. Treasury yields for securities with terms approximating the expected term of the option.
	A summary of share option activity under the 2011 Plan as of September 30, 2013 and changes during the nine months ended September 30, 2013 is presented below:
		Number			Weighted-	Average	Aggregate
		of Options			Average	Remaining	Intrinsic
					Exercise	Contractual	Value
					Price ($)	Term	$0
						(Years)
	Outstanding at December 31, 2012	247,650			9.59	8	$	2,015
	Exercised	(70,900	)		9.51
	Forfeited or expired	(97,375	)		10.74
	Outstanding at September 30, 2013	79,375			8.26	6.9	2,065
	Exercisable at September 30, 2013	44,375			8.03	6.9	1,164
	Vested or Expected to Vest at September 30, 2013	78,913			8.25	6.9	2,053
	The total intrinsic value of share options exercised during the nine months ended September 30, 2013 was $1.2 million.
	As of September 30, 2013 and 2012, there was $0.1 million and $0.7 million, respectively, of total unrecognized compensation cost related to options expected to be recognized over a weighted-average period of 0.8 years and 2.2 years, respectively.
	Performance Share Awards
	During 2013 and 2012, the Company granted certain senior-level executives restricted stock units that vest based on market and service conditions as part of a long-term incentive plan, which are referred to herein as performance share awards. The number of shares of common stock underlying each award is determined at the end of a three-year performance period. In order to vest, the senior level executive must still be employed by the Company, with certain contractual exclusions, at the end of the performance period. At the end of the performance period, the percentage of the stock units that will vest will be determined by ranking the Company’s total shareholder return compared to the total shareholder return of the 11 peer companies identified in the plan. Based on the level of performance, between 0% and 200% of the award may vest. Within 60 days after vesting, the shares underlying the award will be issued to the participant. In the event of a change in control of the Company or the disability or death of a participant, the payout of any award is limited to a pro-rated portion of such award based upon a performance assessment prior to the change-in-control date or date of disability or death.
	The market condition requirements are reflected in the grant date fair value of the award, and the compensation expense for the award will be recognized on a straight-line basis over the performance period assuming that the requisite service is rendered regardless of whether the market conditions are achieved.
	The grant date fair value of the performance share awards was determined through the use of a Monte Carlo simulation model, which utilizes multiple input variables that determine the probability of satisfying the market condition requirements. A summary of the variables used is presented below for grants occurring in the respective periods:
		Weighted-Average at Grant Date for Nine Months Ended September 30, 2013		Weighted-Average at Grant Date for Nine Months Ended September 30, 2012
	Expected volatility factor	0.41		0.39
	Risk free interest rate	0.32	%	0.45	%
	Expected term (in years)	2.72		2.74
	Expected dividend yield	—	%	—	%
	The volatility was based upon a weighted average of the volatility for the Company and the most recent volatility of the peer group. The peer group used to calculate volatility is consistent with the group used for the traditional employee stock options. The Company chose to use historical volatility to value these awards because historical stock prices were used to develop the correlation coefficients between the Company and each of the peer companies within the peer group in order to model stock price movements. The volatilities used were calculated over the most recent period, which aligned with the performance period at the grant date for each respective grant. The risk-free interest rate was based on the implied yield available on U.S. Treasury zero-coupon issues with remaining terms equivalent to the remaining performance period. The Company does not intend to pay dividends on its common stock in the foreseeable future. Accordingly, the Company used a dividend yield of zero in its models for the nine months ended September 30, 2013 and 2012.
	The following table summarizes the Company’s performance share awards for nine months ended September 30, 2013:
		Number of Awards			Weighted-Average Fair Value at Grant Date ($)
	Outstanding at December 31, 2012	280,907			20.3
	Granted	109,950			25.94
	Vested	—			—
	Forfeited	(79,950	)		21.76
	Outstanding at September 30, 2013	310,907			21.92
	As of September 30, 2013 and 2012, there was $6.3 million and $7.5 million of total unrecognized compensation cost related to performance share awards. The unrecognized cost is expected to be recognized over 1.7 years and 2.3 years, respectively.

Tax_Receivable_Agreement

Tax Receivable Agreement	9 Months Ended
	Sep. 30, 2013
Tax Receivable Agreement [Abstract]
Tax Receivable Agreement	Tax Receivable Agreement
	On June 1, 2011, the Company completed its initial public offering of common stock, or IPO. In connection with the IPO, the Company entered into a Tax Receivable Agreement (TRA) and thereby distributed immediately prior to the completion of the IPO to the holders of common stock as of such time, or the Pre-IPO Stockholders, the right to receive an amount equal to 90% of the cash savings in federal income tax realized by the Company by virtue of the use of the federal net operating loss, deferred interest deductions, and alternative minimum tax credits held by the Company as of March 31, 2011, which is defined as the Pre-IPO NOL. Cash tax savings generally will be computed by comparing the actual federal income tax liability to the amount of such taxes that the Company would have been required to pay had such Pre-IPO NOLs not been available. Upon consummation of the IPO and execution of the TRA, the Company recorded a liability with an offsetting reduction to additional paid-in-capital. The amount and timing of payments under the TRA will depend upon a number of factors, including, but not limited to, the amount and timing of taxable income generated in the future and any future limitations that may be imposed on the Company's ability to use the Pre-IPO NOLs. The term of the TRA will continue until the first to occur of (a) the full payment of all amounts required under the agreement with respect to utilization or expiration of all of the Pre-IPO NOLs, (b) the end of the taxable year including the tenth anniversary of the IPO or (c) a change in control of the Company.
	In accordance with the TRA, the Company is required to submit a Tax Benefit Schedule showing the proposed TRA payout amount to the Stockholder Representatives within 45 calendar days after the Company files its tax return. Stockholder Representatives are defined as Indigo Pacific Partners, LLC and OCM FIE, LLC, representing the two largest ownership interests of pre-IPO shares. The Tax Benefit Schedule shall become final and binding on all parties unless a Stockholder Representative, within 45 calendar days after receiving such schedule, provides the Company with notice of a material objection to such schedule. If the parties, for any reason, are unable to successfully resolve the issues raised in any notice within 30 calendar days of receipt of such notice, the Company and the Stockholder Representatives shall employ the Reconciliation procedures. If the Tax Benefit Schedule is accepted, the Company has five days after the acceptance to make payments to the pre-IPO shareholders. Pursuant to the TRA's Reconciliation procedures, any disputes that cannot be settled amicably, are settled by arbitration conducted by a single arbitrator jointly selected by both parties.
	During the second quarter of 2012, the Company paid $27.2 million, or 90% of the 2011 tax savings realized from the utilization of NOLs, including $0.3 million of applicable interest. During 2012, management adjusted for an immaterial error in the original estimate of the liability. This adjustment reduced the liability with an offset to additional paid in capital. As of December 31, 2012, the Company estimated the TRA liability remaining to be $8.0 million.
	During the third quarter of 2013, the Company filed an amended 2009 income tax return in order to correct its NOL carry forward as of December 31, 2009. As a result, the Company's NOL carry forward as of March 31, 2011 was consequently reduced by $7.8 million, which corresponds to a reduction in the estimated TRA benefit of $2.4 million with an offset to additional paid in capital. On September 13, 2013, the Company filed its 2012 federal income tax return, and on October 14, 2013 the Company submitted Tax Benefit Schedule to the Stockholder representatives. As of September 30, 2013, the Company estimated the TRA liability to be $5.6 million.

Subsequent_Events_Notes

Subsequent Events (Notes)	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	On October 1, 2013, the Company entered into agreements with each of Pratt & Whitney (P&W), a division of United Technologies Corp., and International Aero Engines AG (IAE) for the provision and servicing of engines to power its fleet of Airbus A320-family aircraft. The agreement with Pratt & Whitney covers provisioning of PW1100G-JM engines to power the Company’s order (including direct leased aircraft) for 55 A320neo family aircraft, of which the Company is scheduled to begin taking delivery in 2015. The Company and Pratt & Whitney also entered into a corresponding maintenance service agreement covering 119 engines, including spare engines. The agreement with IAE covers provisioning of V2500-series engines to power 45 of the existing A320 family aircraft on order, with deliveries commencing in 2015, and a maintenance service agreement covering up to 96 engines, including spare engines. As part of the transaction, the Company also amended and restated its existing maintenance service agreement with IAE, which agreement currently covers 147 engines, including spare engines. Commitments disclosed within Note 7, "Commitments and Contingencies," are inclusive of additional commitments resulting from the agreement with IAE and P&W.
	On October 15, 2013, the Company had an aircraft experience an engine failure shortly after takeoff. The aircraft immediately returned to the airport, landed safely and the passengers and crew safely disembarked from the aircraft. The airframe and engine incurred damage as a result of the failure. We are working jointly with the FAA and the NTSB to determine the cause of the engine failure, and until the investigation has been completed, and liability determined, it is difficult to assess what the direct financial impact to the Company will be. We believe the total impact to the statement of operations from this incident could be up to $10 million which includes expenses related to repairing the damage to the aircraft involved, the write-off of the deferred heavy maintenance related to the engine, and other operating expenses. It is not certain whether any portion of these expenses will ultimately be recovered through insurance or other related claims.

Net_Income_per_Share_Tables

Net Income per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Computation of basic and diluted earnings per common share	The following table sets forth the computation of basic and diluted earnings per common share:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2013		2012		2013		2012
		(in thousands, except per share amounts)
	Numerator
	Net income	$	61,103	$	30,884	$	133,725	$	88,894
	Denominator
	Weighted-average shares outstanding, basic	72,632		72,427		72,571		72,367
	Effect of dilutive stock awards	371		231		363		214
	Adjusted weighted-average shares outstanding, diluted	73,003		72,658		72,934		72,581
	Net Income per Share
	Basic earnings per common share	$	0.84	$	0.43	$	1.84	$	1.23
	Diluted earnings per common share	$	0.84	$	0.43	$	1.83	$	1.22
	Potentially dilutive amounts excluded from calculations:
	Stock options and restricted stock units	1		—		1		—

Accrued_Liabilities_Tables

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2013
Payables and Accruals [Abstract]
Accrued liabilities included in other current liabilities	Other current liabilities as of September 30, 2013 and December 31, 2012 consist of the following:
		September 30, 2013		December 31, 2012
		(in thousands)
	Federal excise and other passenger taxes and fees payable	$	24,051	$	23,401
	Aircraft maintenance	23,784		22,319
	Salaries and wages	22,357		21,057
	Airport expenses	16,757		16,024
	Fuel	12,994		11,219
	Aircraft and facility rent	6,133		8,020
	Tax receivable agreement	5,643		7,987
	Other	18,051		11,287
	Accrued liabilities	$	129,770	$	121,314

Financial_Instruments_and_Risk1

Financial Instruments and Risk Management (Tables)	9 Months Ended
	Sep. 30, 2013
Investments, All Other Investments [Abstract]
Components of aircraft fuel expense	The following table summarizes the components of aircraft fuel expense for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013		2012
		(in thousands)
	Into-plane fuel cost	$	143,978		$	123,517		$	402,066	$	351,057
	Settlement losses (gains)	6,663			(580		)	6,348		(543		)
	Unrealized mark-to-market losses (gains)	(5,655		)	(921		)	3,489		460
	Aircraft fuel	$	144,986		$	122,016		$	411,903	$	350,974

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Future minimum lease payments under noncancelable operating leases	Future minimum lease payments under noncancelable operating leases as of September 30, 2013 and the periods in which payments are due were as follows:
		Operating Lease Obligations
		(in thousands)
	Remainder of 2013	$	47,411
	2014	188,817
	2015	188,492
	2016	181,369
	2017	157,756
	2018 and thereafter	574,141
	Total minimum lease payments	$	1,337,986
Employee groups and status of the collective bargaining agreements	The table below sets forth our employee groups and status of the collective bargaining agreements as of September 30, 2013.
	Employee Groups		Representative	Amendable Date	Percentage of Workforce
	Pilots		Air Line Pilots Association, International (ALPA)	August 2015	24%
	Flight Attendants		Association of Flight Attendants (AFA-CWA)	Aug-07	34%
	Dispatchers		Transport Workers Union (TWU)	Aug-18	1%

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	Assets and liabilities measured at gross fair value on a recurring basis are summarized below:
		Fair Value Measurements as of September 30, 2013
		Total			Level		Level		Level
					1		2		3
		(in millions)
	Cash and cash equivalents	$	540.2		$	540.2	$	—	$	—
	Jet fuel swaps	1.7			—		1.7		—
	Total assets	$	541.9		$	540.2	$	1.7	$	—
	Jet fuel swaps	$	4.9		$	—	$	4.9	$	—
	Total liabilities	$	4.9		$	—	$	4.9	$	—
		Fair Value Measurements as of December 31, 2012
		Total			Level		Level		Level
					1		2		3
		(in millions)
	Cash and cash equivalents	$	416.8		$	416.8	$	—	$	—
	Jet fuel options	0.3			—		—		0.3
	Total assets	$	417.1		$	416.8	$	—	$	0.3
	Total liabilities	$	—		$	—	$	—	$	—
Assets and liabilities measured at fair value on a recuring basis using significant unobservable inputs (level 3)	The following table presents the Company’s activity for assets and liabilities measured at gross fair value on a recurring basis using significant unobservable inputs (Level 3):
		Jet Fuel Option Activity for the Three Months Ended September 30, 2013
		(in millions)
	Balance at June 30, 2013	$	(0.3	)
	Total realized or unrealized gains (losses) included in earnings, net	0.5
	Settlements, net	(0.2		)
	Balance at September 30, 2013	$	—
		Jet Fuel Option Activity for the Nine Months Ended September 30, 2013
		(in millions)
	Balance at December 31, 2012	$	0.3
	Total realized or unrealized gains (losses) included in earnings, net	0.1
	Settlements, net	(0.4		)
	Balance at September 30, 2013	$	—

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of the status of the Company's restricted stock shares	A summary of the status of the Company’s restricted stock shares (restricted stock awards and restricted stock unit awards) as of September 30, 2013 and changes during the nine months ended September 30, 2013 is presented below:
		Number of Shares			Weighted-Average
					Grant Date Fair Value ($)
	Outstanding at December 31, 2012	449,629			16.93
	Granted	135,005			25.9
	Vested	(165,745	)		13.15
	Forfeited	(89,744	)		19.09
	Outstanding at September 30, 2013	329,145			21.94
Summary of share option activity	A summary of share option activity under the 2011 Plan as of September 30, 2013 and changes during the nine months ended September 30, 2013 is presented below:
		Number			Weighted-	Average	Aggregate
		of Options			Average	Remaining	Intrinsic
					Exercise	Contractual	Value
					Price ($)	Term	$0
						(Years)
	Outstanding at December 31, 2012	247,650			9.59	8	$	2,015
	Exercised	(70,900	)		9.51
	Forfeited or expired	(97,375	)		10.74
	Outstanding at September 30, 2013	79,375			8.26	6.9	2,065
	Exercisable at September 30, 2013	44,375			8.03	6.9	1,164
	Vested or Expected to Vest at September 30, 2013	78,913			8.25	6.9	2,053
Multiple input variables of performance share awards	The grant date fair value of the performance share awards was determined through the use of a Monte Carlo simulation model, which utilizes multiple input variables that determine the probability of satisfying the market condition requirements. A summary of the variables used is presented below for grants occurring in the respective periods:
		Weighted-Average at Grant Date for Nine Months Ended September 30, 2013		Weighted-Average at Grant Date for Nine Months Ended September 30, 2012
	Expected volatility factor	0.41		0.39
	Risk free interest rate	0.32	%	0.45	%
	Expected term (in years)	2.72		2.74
	Expected dividend yield	—	%	—	%
Performance share award activity	The following table summarizes the Company’s performance share awards for nine months ended September 30, 2013:
		Number of Awards			Weighted-Average Fair Value at Grant Date ($)
	Outstanding at December 31, 2012	280,907			20.3
	Granted	109,950			25.94
	Vested	—			—
	Forfeited	(79,950	)		21.76
	Outstanding at September 30, 2013	310,907			21.92

Special_Charges_and_Credits_De

Special Charges and Credits (Details) (USD $)	3 Months Ended	0 Months Ended	9 Months Ended	24 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Jan. 31, 2012	Sep. 30, 2012	Dec. 31, 2012
	Third Quarter 2013 Secondary Offering [Member]	January 25, 2012 Secondary Offering [Member]	January 25, 2012 Secondary Offering [Member]	January 25, 2012 Secondary Offering [Member]
Restructuring Cost and Reserve [Line Items]
Shares sold by certain stockholders in secondary offering (in shares)	12,070,920	12,650,000
Payments of stock issuance costs	$0.40		$0.50	$1.30
Stock issuance cost reimbursements				$0.60

Net_Income_per_Share_Details

Net Income per Share (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator
Net income	$61,103	$30,884	$133,725	$88,894
Denominator
Weighted-average shares outstanding, basic (in shares)	72,632	72,427	72,571	72,367
Effect of dilutive nonvested stock awards (in shares)	371	231	363	214
Adjusted weighted-average shares outstanding, diluted (in shares)	73,003	72,658	72,934	72,581
Net Income per Share
Basic earnings per common share (in dollars per share)	$0.84	$0.43	$1.84	$1.23
Diluted earnings per common share (in dollars per share)	$0.84	$0.43	$1.83	$1.22
Antidilutive awards excluded from computation of earnings per common share (in shares)	1	0	1	0

Accrued_Liabilities_Details

Accrued Liabilities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Federal excise and other passenger taxes and fees payable	$24,051	$23,401
Aircraft maintenance	23,784	22,319
Salaries and wages	22,357	21,057
Airport expenses	16,757	16,024
Fuel	12,994	11,219
Aircraft and facility rent	6,133	8,020
Tax receivable agreement	5,643	7,987
Other	18,051	11,287
Accrued liabilities	$129,770	$121,314

Financial_Instruments_and_Risk2

Financial Instruments and Risk Management (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
					Fuel [Member]	Fuel [Member]
						gal
Investments, All Other Investments [Abstract]
Into-plane fuel cost	$143,978	$123,517	$402,066	$351,057
Settlement losses (gains)	6,663	-580	6,348	-543
Unrealized mark-to-market losses (gains)	-5,655	-921	3,489	460
Aircraft fuel	$144,986	$122,016	$411,903	$350,974
Derivative [Line Items]
Nonmonetary notional amount (in gallons)						7,800,000
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage, Next Fiscal Quarter					21.00%
Nonmonetary notional amount, percent of required need, coverage, next fiscal year						5.00%
Weighted average ceiling price (in dollars per gallon)						3.09
Weighted average floor price (in dollars per gallon)						2.84

Commitments_and_Contingencies_1

Commitments and Contingencies - Commitments (Details) (USD $)

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Jun. 30, 2012

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

In Millions, unless otherwise specified

aircraft

Aircraft and Related Flight Equipment [Member]

Reservation System Provider [Member]

Airbus A320 Family [Member]

Airbus A320, current model [Member]

Airbus A321 [Member]

Airbus A320 NEO [Member]

Airbus A321 NEO [Member]

Airbus A319 [Member]

Airbus A319 [Member]

V2500 SelectOne Engine [Member]

PurePower PW1100G-JM Engine [Member]

aircraft

aircraft

aircraft

aircraft

aircraft

aircraft

aircraft_engine

aircraft_engine

Commitments and Contingencies Disclosure [Abstract]

Number of spare aircraft engines ordered (in aircraft engine)

6

9

Unrecorded Unconditional Purchase Obligation [Line Items]

Number of Aircraft with Extended Leases (in aircraft)

14

Additional Lease Commitments due to Extended Aircraft Leases, Due 2017 and thereafter

$72.80

Number of Additional Aircraft Ordered (in aircraft)

20

Number of Aircraft Originally Ordered (in aircraft)

95

Number of Aircraft Whose Aircraft Type Was Converted

10

5

Number of aircraft ordered (in aircraft)

115

40

25

45

5

Number of Direct Leased Aircraft Ordered from a Third Party (in aircraft)

5

Number of Aircraft with Secured Financing Commitments Scheduled for Delivery (in aircraft)

10

Number of Aircraft without Secured Financing Commitments Scheduled for Delivery (in aircraft)

105

Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]

Committed expenditures, remainder of 2013

136

0.9

Committed expenditures, 2014

412

3.9

Committed expenditures, 2015

794

3.9

Committed expenditures, 2016

640

3.9

Committed expenditures, 2017

816

3.9

Committed expenditures, 2018 and beyond

$2,743

$2.60

Commitments_and_Contingencies_2

Commitments and Contingencies - Sale Leaseback Transactions Aircraft (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
	aircraft_engine
	aircraft
Commitments and Contingencies Disclosure [Abstract]
Number of aircrafts delivered	6
Number of aircrafts financed with direct operating leases	2
Number of spare aircraft engines entered into sale and leaseback agreement	1
Aircraft [Member]
Sale Leaseback Transaction [Line Items]
Number of aircraft entered into sale and leaseback agreement	4
Sale leaseback transaction on aircraft, net deferred gain (loss)	-1.4
Sale leaseback transaction on aircraft, refund in pre-delivery deposits	21.5

Commitments_and_Contingencies_3

Commitments and Contingencies - Future Minimum Lease Payments Under Noncancelable Operating Leases (Details) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Future Minimum Payments Due, Remainder of 2013	$47,411
Future Minimum Payments Due, 2014	188,817
Future Minimum Payments Due, 2015	188,492
Future Minimum Payments Due, 2016	181,369
Future Minimum Payments Due, 2017	157,756
Future Minimum Payments Due, 2018 and thereafter	574,141
Total minimum lease payments	$1,337,986

Commitments_and_Contingencies_4

Commitments and Contingencies - Fixed Maintenance Reserve Payments (Details) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
Fixed maintenance reserve payments, future estimated payments due, the remainder of 2013	$1.80
Fixed maintenance reserve payments, future estimated payments due, 2014	7.4
Fixed maintenance reserve payments, future estimated payments due, 2015	7.6
Fixed maintenance reserve payments, future estimated payments due, 2016	8
Fixed maintenance reserve payments, future estimated payments due, 2017	7.4
Fixed maintenance reserve payments, future estimated payments due, 2018 and beyond	$24.20

Commitments_and_Contingencies_5

Commitments and Contingencies - Credit Card Processing Arrangements (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Cash collateral required for credit card transactions as a percentage of air traffic liability, prior to amendment	100.00%
Cash holdback for credit card transactions	$0	$0
Maximum potential exposure to cash holdbacks from credit card processors	$203,800,000	$144,800,000

Commitments_and_Contingencies_6

Commitments and Contingencies - Employees (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			Unionized Employees Concentration Risk [Member]	Unionized Employees Concentration Risk [Member]	Unionized Employees Concentration Risk [Member]	Unionized Employees Concentration Risk [Member]
			Number of Employees, Total [Member]	Number of Employees, Total [Member]	Number of Employees, Total [Member]	Number of Employees, Total [Member]
				Association of Flight Attendants [Member]	Air Line Pilots Association, International [Member]	Transport Workers Union [Member]
Multiemployer Plans [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			59.00%	34.00%	24.00%	1.00%
Accrued health care claims	$2.10	$1.90

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (Fair Value, Measurements, Recurring [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$540.20	$416.80
Total assets	541.9	417.1
Total liabilities	4.9	0
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	540.2	416.8
Total assets	540.2	416.8
Total liabilities	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	1.7	0
Total liabilities	4.9	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	0	0.3
Total liabilities	0	0
Jet fuel swaps [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1.7
Derivative liabilities	4.9
Jet fuel swaps [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Derivative liabilities	0
Jet fuel swaps [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1.7
Derivative liabilities	4.9
Jet fuel swaps [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Derivative liabilities	0
Option contracts [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.3
Option contracts [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0
Option contracts [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0
Option contracts [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		$0.30

Fair_Value_Measurements_Assets1

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Details) (Option contracts [Member], USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Option contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	($0.30)	$0.30
Total realized or unrealized gains (losses) included in earnings, net	0.5	0.1
Settlements, net	-0.2	-0.4
Balance at September 30, 2013	$0	$0

StockBased_Compensation_Share_

Stock-Based Compensation - Share Option Activity (Details) (Stock Options [Member], USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding (in shares)	247,650
Exercised (in shares)	-70,900
Forfeited or expired (in shares)	-97,375
Outstanding (in shares)	79,375		247,650
Exercisable (in shares)	44,375
Vested or expected to vest (in shares)	78,913
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, weighted-average exercise price (in dollars per share)	$9.59
Exercised, weighted-average exercise price (in dollars per share)	$9.51
Forfeited or expired, weighted-average exercise price (in dollars per share)	$10.74
Outstanding, weighted-average exercise price (in dollars per share)	$8.26		$9.59
Exercisable, weighted-average exercise price (in dollars per share)	$8.03
Vested or expected to vest, weighted-average exercise price (in dollars per share)	$8.25
Outstanding, average remaining contractual term (in years)	6 years 10 months 24 days		8 years
Exercisable, average remaining contractual term (in years)	6 years 10 months 24 days
Vested or expected to vest, average remaining contractual term	6 years 10 months 24 days
Outstanding, aggregate intrinsic value	$2,065,000		$2,015,000
Exercisable, aggregate intrinsic value	1,164,000
Vested or expected to vest, aggregate intrinsic value	2,053,000
Total instrinsic value of share options exercised	1,200,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$100,000	$700,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	10 months 6 days	2 years 2 months 19 days

StockBased_Compensation_Restri

Stock-Based Compensation - Restricted Stock Activity (Details) (USD $)	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Restricted Stock and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding (in shares)	449,629
Granted (in shares)	135,005	377,942
Vested (in shares)	-165,745
Forfeited (in shares)	-89,744
Outstanding (in shares)	329,145
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, weighted-average grant date fair value (in dollars per share)	$16.93
Granted, weighted-average grant date fair value (in dollars per share)	$25.90
Vested, weighted-average grant date fair value (in dollars per share)	$13.15
Forfeited, weighted-average grant date fair value (in dollars per share)	$19.09
Outstanding, weighted-average grant date fair value (in dollars per share)	$21.94
Total fair value of shares vested	$4.10	$3.60
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$6.10	$6.50
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	2 years 9 months 18 days	3 years 5 months 4 days

StockBased_Compensation_Simula

Stock-Based Compensation - Simulation Model Input Variables (Details) (Performance Shares Awards [Member])	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Performance Shares Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility factor	41.00%	39.00%
Risk free interest rate	0.32%	0.45%
Expected term (in years)	2 years 8 months 19 days	2 years 8 months 26 days
Expected dividend yield	0.00%	0.00%

StockBased_Compensation_Perfor

Stock-Based Compensation - Performance Share Awards (Details) (Performance Shares Awards [Member], USD $)	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Performance Shares Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding (in shares)	280,907
Granted (in shares)	109,950
Vested (in shares)	0
Forfeited (in shares)	-79,950
Outstanding (in shares)	310,907
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, weighted-average grant date fair value (in dollars per share)	$20.30
Granted, weighted-average grant date fair value (in dollars per share)	$25.94
Vested, weighted-average grant date fair value (in dollars per share)	$0
Forfeited, weighted-average grant date fair value (in dollars per share)	$21.76
Outstanding, weighted-average grant date fair value (in dollars per share)	$21.92
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$6.30	$7.50
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 8 months 4 days	2 years 3 months

StockBased_Compensation_Narrat

Stock-Based Compensation - Narrative (Details) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

In Millions, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2007

Sep. 30, 2013

Dec. 31, 2012

9-May-11

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

2005 Stock Plan [Member]

2011 Equity Incentive Award Plan [Member]

2011 Equity Incentive Award Plan [Member]

2011 Equity Incentive Award Plan [Member]

Restricted Stock and Restricted Stock Units [Member]

Stock Options [Member]

Stock Options [Member]

Performance Shares Awards [Member]

Performance Shares Awards [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares authorized for issue (in shares)

2,500,000

3,000,000

Shares available for future issuance (in shares)

2,709,523

2,689,490

Award vesting percentage per year (as a percent)

25.00%

Award vesting period

4 years

Contractual term

10 years

Grants in period (in shares)

0

0

Share-based compensation cost

$1.20

$1.30

$4

$3

Share-based compensation cost, tax benefit recognized in income

0.4

0.5

1.5

1.1

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized

$0.10

$0.70

$6.30

$7.50

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition

10 months 6 days

2 years 2 months 19 days

1 year 8 months 4 days

2 years 3 months

Potential vesting percentage, minimum

0.00%

Potential vesting percentage, maximum

200.00%

Period for share issuance after vesting

60 days

Expected dividend yield

0.00%

0.00%

Tax_Receivable_Agreement_Detai

Tax Receivable Agreement (Details) (USD $)	3 Months Ended
	Sep. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Mar. 31, 2012
				owner
Tax Receivable Agreement [Abstract]
Percentage of cash savings from pre-initial public offering net operating loss due to pre-initial public offering stockholders				90.00%
Tax receivable agreement, tax benefit schedule days to submission				45 days
Tax receivable agreement, number of largest owners pre initial public offering				2
Tax receivable agreement, tax benefit schedule days to response				45 days
Tax receivable agreement, tax benefit schedule days to resolve notice				30 days
Tax receivable agreement, tax benefit schedule days to payment after acceptance				5 days
Cash payment including interest to pre-initial public offering stockholders pursuant to tax receivable agreement		$27,200,000
Percentage of cash savings from pre-initial public offering net operating loss paid to pre-initial public offering stockholders		90.00%
Interest included in cash payment to pre-initial public offering stockholders pursuant to tax receivable agreement		300,000
Tax receivable agreement	5,643,000		7,987,000
Operating loss carryforwards, reduction	7,800,000
Reduction in TRA liability	$2,400,000

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	Oct. 15, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified	Subsequent Event [Member]	Airbus A320 Family [Member]	Airbus A320 Family [Member]	Airbus A320 NEO Family [Member]	PurePower PW1100G-JM Engine [Member]	PurePower PW1100G-JM Engine [Member]	V2500 SelectOne Engine [Member]	V2500 SelectOne Engine [Member]
		aircraft	Subsequent Event [Member]	Subsequent Event [Member]	aircraft_engine	Subsequent Event [Member]	aircraft_engine	Subsequent Event [Member]
			aircraft	aircraft		aircraft_engine		aircraft_engine
Subsequent Event [Line Items]
Number of spare aircraft engines ordered (in aircraft engine)					9	119	6
Number of aircraft ordered (in aircraft)		115	45	55
Number of aircraft engines ordered with maintenance service agreements, future deliveries (in aircraft engine)								96
Number of aircraft engines ordered with maintenance service agreements, including future deliveries (in aircraft engine)								147
Loss contingency, range of possible loss, maximum	$10