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Fair Value Measurements - Measured on Recurring Basis (Details) - USD ($) | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Fuel derivatives: |  |
Option contracts | $ 503,000,000 | $ 134,000,000
Fair Value, Measurements, Recurring |  |
Assets |  |
Treasury bills | 2,150,000,000 | 1,800,000,000
Fuel derivatives: |  |
Interest rate derivatives (see Note 4) | 1,000,000 |
Other available-for-sale securities | 259,000,000 | 259,000,000
Total assets | 17,637,000,000 | 13,727,000,000
Liabilities |  |
Interest rate derivatives (see Note 4) |  | (6,000,000)
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement |  |
Liabilities |  |
Interest rate derivatives (see Note 4) | (3,000,000) |
Fair Value, Measurements, Recurring | Options Held |  |
Fuel derivatives: |  |
Option contracts | 502,000,000 | 134,000,000
Fair Value, Measurements, Recurring | Certificates of deposit |  |
Assets |  |
Investments | 1,000,000 | 46,000,000
Fair Value, Measurements, Recurring | Time deposits |  |
Assets |  |
Investments | 600,000,000 | 425,000,000
Fair Value, Measurements, Recurring | Cash Equivalents |  |
Assets |  |
Cash equivalents | 13,759,000,000 | 10,663,000,000
Fair Value, Measurements, Recurring | Commercial paper |  |
Assets |  |
Cash equivalents | 90,000,000 | 90,000,000
Fair Value, Measurements, Recurring | Certificates of deposit |  |
Assets |  |
Cash equivalents |  | 10,000,000
Fair Value, Measurements, Recurring | Time deposits |  |
Assets |  |
Cash equivalents | 275,000,000 | 300,000,000
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Treasury bills | 2,150,000,000 | 1,800,000,000
Fuel derivatives: |  |
Interest rate derivatives (see Note 4) | 0 |
Other available-for-sale securities | 259,000,000 | 259,000,000
Total assets | 16,168,000,000 | 12,722,000,000
Liabilities |  |
Interest rate derivatives (see Note 4) | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Options Held |  |
Fuel derivatives: |  |
Option contracts | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Certificates of deposit |  |
Assets |  |
Investments | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Time deposits |  |
Assets |  |
Investments | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Cash Equivalents |  |
Assets |  |
Cash equivalents | 13,759,000,000 | 10,663,000,000
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Commercial paper |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Certificates of deposit |  |
Assets |  |
Cash equivalents |  | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Time deposits |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |
Assets |  |
Treasury bills | 0 | 0
Fuel derivatives: |  |
Interest rate derivatives (see Note 4) | 1,000,000 |
Other available-for-sale securities | 0 | 0
Total assets | 967,000,000 | 871,000,000
Liabilities |  |
Interest rate derivatives (see Note 4) | (3,000,000) | (6,000,000)
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Options Held |  |
Fuel derivatives: |  |
Option contracts | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Certificates of deposit |  |
Assets |  |
Investments | 1,000,000 | 46,000,000
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Time deposits |  |
Assets |  |
Investments | 600,000,000 | 425,000,000
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Cash Equivalents |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Commercial paper |  |
Assets |  |
Cash equivalents | 90,000,000 | 90,000,000
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Certificates of deposit |  |
Assets |  |
Cash equivalents |  | 10,000,000
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Time deposits |  |
Assets |  |
Cash equivalents | 275,000,000 | 300,000,000
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |
Assets |  |
Treasury bills | 0 | 0
Fuel derivatives: |  |
Interest rate derivatives (see Note 4) | 0 |
Other available-for-sale securities | 0 | 0
Total assets | 502,000,000 | 134,000,000
Liabilities |  |
Interest rate derivatives (see Note 4) | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Options Held |  |
Fuel derivatives: |  |
Option contracts | 502,000,000 | 134,000,000
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Certificates of deposit |  |
Assets |  |
Investments | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Time deposits |  |
Assets |  |
Investments | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Cash Equivalents |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Commercial paper |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Certificates of deposit |  |
Assets |  |
Cash equivalents |  | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Time deposits |  |
Assets |  |
Cash equivalents | $ 0 | $ 0

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