Financial Instruments and Fair Value Measurements - Additional Information (Detail) - Entity [Domain] - USD ($) shares in Millions, $ in Millions	1 Months Ended	6 Months Ended
Jan. 31, 2015	Jun. 30, 2015
Asset-backed Securities \| Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		1 year
Asset-backed Securities \| Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		40 years
Corporate Debt \| Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		1 year
Corporate Debt \| Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		7 years
CDARS \| Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		1 year
U.S. Government and Other Securities \| Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		1 year
U.S. Government and Other Securities \| Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities		3 years
EETC \| Maximum
Fair Value [Line Items]
Available-for-sale securities maturity, year		2019
Unsecured Debt \| 4.5% Convertible Notes Due 2015
Fair Value [Line Items]
Debt instrument stated interest rate	4.50%	4.50%
Debt instrument principal amount	$ 202	$ 202
Issuance of common stock conversion price	11	11

Available for Sale Investment Maturity Term

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Available for Sale Investment Maturity Year

+ References

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- Definition

Fair Value [Line Items]

+ References

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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- Definition

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

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- Definition

Number of shares issued during the period as a result of the conversion of convertible securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-30)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

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