NEW ACCOUNTING PRONOUNCEMENTS	12 Months Ended
Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
NEW ACCOUNTING PRONOUNCEMENTS	NEW ACCOUNTING PRONOUNCEMENTS AND ACCOUNTING CHANGES On August 28, 2017, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2017-12, Targeted Improvements to Accounting for Hedging Activities. The standard amends the hedge accounting model to enable entities to better portray the economics of their risk management activities in the financial statements and enhance the transparency and understandability of hedge results. The amendments also simplify the application of hedge accounting in certain situations. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted in any interim or annual period. The Company plans to adopt this ASU as of January 1, 2018. See Note 10 for further information on current accounting for financial derivative instruments. The most significant impacts of this ASU on the Company's financial statements is the elimination of the requirement to separately measure and report ineffectiveness for all cash flow hedges in a hedging relationship, as well as a change in classification of premium expense associated with option contracts. The estimate of the cumulative effect of the adjustment to move the reporting of ineffectiveness as of January 1, 2018, to Accumulated other comprehensive income (loss) from Retained earnings, is an approximate $20 million loss, net of taxes. Historically amounts that are paid or received in connection with the purchase or sale of financial derivative instruments (i.e., premium costs of option contracts) have been classified as a component of Other (gains) losses, net, in the Consolidated Statement of Income in the period in which the instrument settles or expires. Under the new ASU, such amounts are reflected as a component of the line item to which the hedge relates, which in the case of the Company’s jet fuel hedges is Fuel and oil expense. This ASU requires prospective adoption. However, as previous hedge accounting rules did not specify the classification of such premium expense, and such provision only consists of a reclassification of expense between income statement line items, the Company will retrospectively apply this reclassification to prior period financial statements in 2018 in order to enhance comparability. For the Company's full year 2017 and 2016 results, the amounts to be reclassified in 2018 are $135 million and $153 million, respectively. On March 10, 2017, the FASB issued ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The standard requires employers to present the service cost component of the net periodic benefit cost in the same income statement line item as other employee compensation costs arising from services rendered during the period. The other components of net benefit cost, including amortization of prior service cost/credit, and settlement and curtailment effects, are to be included in nonoperating expenses. This ASU requires retrospective application and is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The Company thus will reclassify $14 million and $12 million of Salaries, wages, and benefits expense to Other (gains) and losses within the Consolidated Statement of Income for years ended 2017 and 2016, respectively. The Company will adopt this guidance as of January 1, 2018. On January 26, 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The standard simplifies the accounting for goodwill impairment by removing Step 2 of the goodwill impairment test (as defined by the FASB), which requires a hypothetical purchase price allocation (implied fair value of goodwill) to measure impairment loss. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019, with early adoption permitted. The Company does not expect this ASU to have a significant impact on its financial statement presentation or results. On February 25, 2016, the FASB issued ASU No. 2016-02, Leases. The standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted. The guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases (with the exception of short-term leases) at the lease commencement date and recognize expenses on the income statement in a similar manner to the current guidance in Accounting Standards Codification 840, Leases. The lease liability will be measured at the present value of the unpaid lease payments and the right-of-use asset will be derived from the calculation of the lease liability. Lease payments will include fixed and in-substance fixed payments, variable payments based on an index or rate, reasonably certain purchase options, termination penalties, fees paid by the lessee to the owners of a special-purpose entity for restructuring the transaction, and probable amounts the lessee will owe under a residual value guarantee. Lease payments will not include variable lease payments other than those that depend on an index or rate, any guarantee by the lessee of the lessor’s debt, or any amount allocated to non-lease components. The Company has formed a project team to evaluate and implement the standard, and currently believes the most significant impact of this ASU on its accounting will be the balance sheet impact of its aircraft operating leases, which will significantly increase assets and liabilities. See Note 7 for further information on leases. The future lease commitments disclosed in Note 7 include contractual payments due to lessors, but does not consider certain items that the standard requires to be assessed in determining the final asset and liability to be reflected on the Company's balance sheet, such as lease renewal options and potential impairments, nor does it consider the sublease income that is due from third parties (which will be disclosed separately). The Company also has operating leases related to terminal operations space and other real estate leases. Although the real estate leases may also have a substantial impact to the balance sheet, the Company does not expect the leases related to terminal operations space to have a significant impact since variable lease payments, other than those based on an index or rate, are excluded from the measurement of the lease liability. The Company also does not expect the adoption of this ASU to impact any of its existing debt covenants. In addition, the standard eliminates the current build-to-suit lease accounting guidance and could result in derecognition of build-to-suit assets and liabilities that remained on the balance sheet after the end of the construction period. The underlying leases for these facilities will be subject to evaluation under the new standard. The Company anticipates utilizing the modified retrospective transition approach to adopt the standard, which requires application of the new guidance for all periods presented with an option to use certain practical expedients. The Company continues to assess early adoption of this ASU as of an interim period in 2018, and will continue to provide updates to its plans in future periods. On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. Following the FASB's finalization of a one year deferral of this standard, the ASU is now effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The Company will adopt the ASU in first quarter 2018. The most significant impact of this ASU on the Company's accounting will be the elimination of the incremental cost method for frequent flyer accounting, which will require the Company to re-value its liabilities associated with Customer flight points with a relative fair value approach, resulting in a significant increase in the liabilities. The Company's liabilities associated with these flight points were $59 million at December 31, 2017, and the Company currently estimates that applying a relative fair value would increase the liabilities by approximately $1.0 billion to $1.2 billion. The adoption of the new standard is also expected to result in different income statement classification for certain types of revenues which are currently classified as Other revenues, but under the new ASU would be included in Passenger revenues, and certain expenses, which are currently classified as Other operating expenses, but under the new ASU would be offset against Passenger revenues. Based on the Company's full year 2017 and 2016 results, the amounts to be reclassified from Other revenues to Passenger revenues would have been $638 million and $610 million, respectively. For full year 2017 and 2016, the amounts to be reclassified from Other operating expenses to be offset against Passenger revenues would have been approximately $40 million in each year. The estimated impact of this ASU is expected to be a less than one percent reduction to Operating revenues for both full year 2017 and 2016, and it will not impact any of the Company's existing debt covenants. The Company will adopt the standard as of January 1, 2018, utilizing the full retrospective method of adoption allowed by the standard, in order to provide for comparative results in all periods presented. The Company is in the process of completing its analysis of information necessary to recast prior period results, however it does not believe there are any remaining significant implementation topics associated with the adoption of this ASU that have not yet been addressed.

NEW ACCOUNTING PRONOUNCEMENTS AND ACCOUNTING CHANGES

On August 28, 2017, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2017-12, Targeted Improvements to Accounting for Hedging Activities. The standard amends the hedge accounting model to enable entities to better portray the economics of their risk management activities in the financial statements and enhance the transparency and understandability of hedge results. The amendments also simplify the application of hedge accounting in certain situations. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted in any interim or annual period. The Company plans to adopt this ASU as of January 1, 2018. See Note 10 for further information on current accounting for financial derivative instruments. The most significant impacts of this ASU on the Company's financial statements is the elimination of the requirement to separately measure and report ineffectiveness for all cash flow hedges in a hedging relationship, as well as a change in classification of premium expense associated with option contracts. The estimate of the cumulative effect of the adjustment to move the reporting of ineffectiveness as of January 1, 2018, to Accumulated other comprehensive income (loss) from Retained earnings, is an approximate $20 million loss, net of taxes. Historically amounts that are paid or received in connection with the purchase or sale of financial derivative instruments (i.e., premium costs of option contracts) have been classified as a component of Other (gains) losses, net, in the Consolidated Statement of Income in the period in which the instrument settles or expires. Under the new ASU, such amounts are reflected as a component of the line item to which the hedge relates, which in the case of the Company’s jet fuel hedges is Fuel and oil expense. This ASU requires prospective adoption. However, as previous hedge accounting rules did not specify the classification of such premium expense, and such provision only consists of a reclassification of expense between income statement line items, the Company will retrospectively apply this reclassification to prior period financial statements in 2018 in order to enhance comparability. For the Company's full year 2017 and 2016 results, the amounts to be reclassified in 2018 are $135 million and $153 million, respectively.

On March 10, 2017, the FASB issued ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The standard requires employers to present the service cost component of the net periodic benefit cost in the same income statement line item as other employee compensation costs arising from services rendered during the period. The other components of net benefit cost, including amortization of prior service cost/credit, and settlement and curtailment effects, are to be included in nonoperating expenses. This ASU requires retrospective application and is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The Company thus will reclassify $14 million and $12 million of Salaries, wages, and benefits expense to Other (gains) and losses within the Consolidated Statement of Income for years ended 2017 and 2016, respectively. The Company will adopt this guidance as of January 1, 2018.

On January 26, 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The standard simplifies the accounting for goodwill impairment by removing Step 2 of the goodwill impairment test (as defined by the FASB), which requires a hypothetical purchase price allocation (implied fair value of goodwill) to measure impairment loss. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019, with early adoption permitted. The Company does not expect this ASU to have a significant impact on its financial statement presentation or results.

On February 25, 2016, the FASB issued ASU No. 2016-02, Leases. The standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted. The guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases (with the exception of short-term leases) at the lease commencement date and recognize expenses on the income statement in a similar manner to the current guidance in Accounting Standards Codification 840, Leases. The lease liability will be measured at the present value of the unpaid lease payments and the right-of-use asset will be derived from the calculation of the lease liability. Lease payments will include fixed and in-substance fixed payments, variable payments based on an index or rate, reasonably certain purchase options, termination penalties, fees paid by the lessee to the owners of a special-purpose entity for restructuring the transaction, and probable amounts the lessee will owe under a residual value guarantee. Lease payments will not include variable lease payments other than those that depend on an index or rate, any guarantee by the lessee of the lessor’s debt, or any amount allocated to non-lease components.

The Company has formed a project team to evaluate and implement the standard, and currently believes the most significant impact of this ASU on its accounting will be the balance sheet impact of its aircraft operating leases, which will significantly increase assets and liabilities. See Note 7 for further information on leases. The future lease commitments disclosed in Note 7 include contractual payments due to lessors, but does not consider certain items that the standard requires to be assessed in determining the final asset and liability to be reflected on the Company's balance sheet, such as lease renewal options and potential impairments, nor does it consider the sublease income that is due from third parties (which will be disclosed separately). The Company also has operating leases related to terminal operations space and other real estate leases. Although the real estate leases may also have a substantial impact to the balance sheet, the Company does not expect the leases related to terminal operations space to have a significant impact since variable lease payments, other than those based on an index or rate, are excluded from the measurement of the lease liability. The Company also does not expect the adoption of this ASU to impact any of its existing debt covenants.

In addition, the standard eliminates the current build-to-suit lease accounting guidance and could result in derecognition of build-to-suit assets and liabilities that remained on the balance sheet after the end of the construction period. The underlying leases for these facilities will be subject to evaluation under the new standard.

The Company anticipates utilizing the modified retrospective transition approach to adopt the standard, which requires application of the new guidance for all periods presented with an option to use certain practical expedients. The Company continues to assess early adoption of this ASU as of an interim period in 2018, and will continue to provide updates to its plans in future periods.

On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. Following the FASB's finalization of a one year deferral of this standard, the ASU is now effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The Company will adopt the ASU in first quarter 2018. The most significant impact of this ASU on the Company's accounting will be the elimination of the incremental cost method for frequent flyer accounting, which will require the Company to re-value its liabilities associated with Customer flight points with a relative fair value approach, resulting in a significant increase in the liabilities. The Company's liabilities associated with these flight points were $59 million at December 31, 2017, and the Company currently estimates that applying a relative fair value would increase the liabilities by approximately $1.0 billion to $1.2 billion. The adoption of the new standard is also expected to result in different income statement classification for certain types of revenues which are currently classified as Other revenues, but under the new ASU would be included in Passenger revenues, and certain expenses, which are currently classified as Other operating expenses, but under the new ASU would be offset against Passenger revenues. Based on the Company's full year 2017 and 2016 results, the amounts to be reclassified from Other revenues to Passenger revenues would have been $638 million and $610 million, respectively. For full year 2017 and 2016, the amounts to be reclassified from Other operating expenses to be offset against Passenger revenues would have been approximately $40 million in each year. The estimated impact of this ASU is expected to be a less than one percent reduction to Operating revenues for both full year 2017 and 2016, and it will not impact any of the Company's existing debt covenants. The Company will adopt the standard as of January 1, 2018, utilizing the full retrospective method of adoption allowed by the standard, in order to provide for comparative results in all periods presented. The Company is in the process of completing its analysis of information necessary to recast prior period results, however it does not believe there are any remaining significant implementation topics associated with the adoption of this ASU that have not yet been addressed.