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Fair Value Measurements - Measured on Recurring Basis (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Jun. 30, 2016 | Dec. 31, 2015
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset | [1] | $ 790 |  | $ 1,937 |
Fuel derivatives: |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability | [1] | (1,770) |  | (3,465) |
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount |  | 0 |  | 0 |
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount |  | 0 |  | 0 |
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount |  | 0 |  | 0 |
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount |  | 0 |  | 0 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net |  | 0 |  | 0 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net |  | 0 |  | 0 |
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Treasury bills |  | 1,098 |  | 1,248 |
Interest rate derivatives (see Note 3) |  | 0 |  | 0 |
Fuel derivatives: |  |  |  |  |
Other available for sale securities |  | 78 |  | 66 |
Total assets |  | 2,862 |  | 2,651 |
Liabilities |  |  |  |  |
Interest rate derivatives (see Note 3) |  | 0 |  | 0 |
Total Liabilities |  | 0 |  | 0 |
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Treasury bills |  | 0 |  | 0 |
Interest rate derivatives (see Note 3) |  | 21 |  | 2 |
Fuel derivatives: |  |  |  |  |
Other available for sale securities |  | 0 |  | 0 |
Total assets |  | 950 |  | 1,437 |
Liabilities |  |  |  |  |
Interest rate derivatives (see Note 3) |  | (44) |  | (49) |
Total Liabilities |  | (392) |  | (823) |
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Treasury bills |  | 0 |  | 0 |
Interest rate derivatives (see Note 3) |  | 0 |  | 0 |
Fuel derivatives: |  |  |  |  |
Other available for sale securities |  | 26 |  | 27 |
Total assets |  | 497 |  | 993 |
Liabilities |  |  |  |  |
Interest rate derivatives (see Note 3) |  | 0 |  | 0 |
Total Liabilities |  | (1,378) |  | (2,642) |
Cash Equivalents | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 1,686 | [2] | 1,337 | [3]
Cash Equivalents | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 | [2] | 0 | [3]
Cash Equivalents | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 | [2] | 0 | [3]
Commercial paper | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Commercial paper | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 270 |  | 200 |
Commercial paper | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 9 |  | 13 |
Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Eurodollar time deposits | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Eurodollar time deposits | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 75 |  | 33 |
Eurodollar time deposits | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 0 |  | 0 |
Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Assets |  |  |  |  |
Investments |  | 0 |  | 0 |
Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Assets |  |  |  |  |
Investments |  | 277 |  | 220 |
Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Assets |  |  |  |  |
Investments |  | 0 |  | 0 |
Swap | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 0 | [6] | 0 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  | 0 | [6] | 0 | [7]
Swap | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 15 | [4] | 38 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 283 | [6] | 931 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  | (348) | [6] | (774) | [7]
Swap | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 0 | [6] | 0 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  | 0 | [6] | 0 | [7]
Options Held | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 0 | [6] | 0 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Liability |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Liability |  | 0 | [6] | 0 | [7]
Options Held | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 0 | [6] | 0 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Liability |  | 0 | [4] | 0 | [5]
Derivative Liability, Fair Value, Gross Liability |  | 0 | [6] | 0 | [7]
Options Held | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 15 | [4] | 10 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 456 | [6] | 956 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Liability |  | (10) | [4] | (26) | [5]
Derivative Liability, Fair Value, Gross Liability |  | (1,368) | [6] | (2,616) | [7]
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Treasury bills |  | 1,098 |  | 1,248 |
Interest rate derivatives (see Note 3) |  | 21 |  | 2 |
Fuel derivatives: |  |  |  |  |
Other available for sale securities |  | 104 |  | 93 |
Total assets |  | 4,309 |  | 5,081 |
Liabilities |  |  |  |  |
Interest rate derivatives (see Note 3) |  | (44) |  | (49) |
Total Liabilities |  | (1,770) |  | (3,465) |
Estimate of Fair Value Measurement [Member] | Cash Equivalents | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 1,686 | [2] | 1,337 | [3]
Estimate of Fair Value Measurement [Member] | Commercial paper | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 270 |  | 200 |
Estimate of Fair Value Measurement [Member] | Certificates of deposit | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 9 |  | 13 |
Estimate of Fair Value Measurement [Member] | Eurodollar time deposits | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Cash equivalents |  | 75 |  | 33 |
Estimate of Fair Value Measurement [Member] | Certificates of deposit | Fair Value, Measurements, Recurring |  |  |  |  |
Assets |  |  |  |  |
Investments |  | 277 |  | 220 |
Estimate of Fair Value Measurement [Member] | Swap | Fair Value, Measurements, Recurring |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 15 | [4] | 38 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 283 | [6] | 931 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  | (348) | [6] | (774) | [7]
Estimate of Fair Value Measurement [Member] | Options Held | Fair Value, Measurements, Recurring |  |  |  |  |
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 15 | [4] | 10 | [5]
Derivative Liability, Fair Value, Gross Asset |  | 456 | [6] | 956 | [7]
Fuel derivatives: |  |  |  |  |
Derivative Asset, Fair Value, Gross Liability |  | (10) | [4] | (26) | [5]
Derivative Liability, Fair Value, Gross Liability |  | $ (1,368) | [6] | $ (2,616) | [7]
[1] | Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note.
[2] | Cash equivalents are primarily composed of money market investments.
[3] | Cash equivalents are primarily composed of money market investments.
[4] | In the unaudited Condensed Consolidated Balance Sheet amounts are presented as a net asset. See Note 3.
[5] | In the unaudited Consolidated Balance Sheet amounts are presented as a net asset. See Note 3.
[6] | In the unaudited Condensed Consolidated Balance Sheet amounts are presented as a net liability. See Note 3.
[7] | In the unaudited Consolidated Balance Sheet amounts are presented as a net liability. See Note 3.

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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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