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Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items] |  |  |
Residual value | 10.00% |  |
Carrying value of computer software | $ 356 | $ 279 |
Advertising expense | $ 220 | 201 | $ 179
Minimum |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Refundable tickets expiration period | 1 year |  |
Recently Issued Accounting Standards |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Restricted cash and cash equivalents | $ 124 | 206 | 320
Recently Issued Accounting Standards | Pension Benefits |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Pension plan investments measured at net asset value per share | 1,800 |  |
Recently Issued Accounting Standards | Short-term Investments |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Investments in certain entities that calculate net asset value per share included in short-term investments | 182 |  |
Computer software |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Depreciation expense related to computer software | $ 108 | $ 93 | $ 81
Aircraft and aircraft spare parts |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Residual value | 10.00% |  |

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- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
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- Definition Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258 + Details
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- Definition Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 + Details
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