Summary of Significant Accounting Policies - Forgivable Loans (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
F9 Pilot Cadet Program [Line Items]
Forgivable loans	$ 16	$ 13
Payments to acquire receivables	16
Financing receivable, after allowance for credit loss, noncurrent	10	16
Accretion (amortization) of discounts and premiums, investments	16	7	$ 1
Proceeds from sale and collection of receivables	3
Financing receivable	1	1
Asset impairment charges	$ 0	$ 0	$ 0

F9 Pilot Cadet Program [Line Items]

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- Definition

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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- Definition

Amortized cost, after allowance for credit loss, of financing receivable classified as current. Excludes net investment in lease.

+ References

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- Definition

Amount, after allowance for credit loss, of financing receivable, classified as noncurrent.

+ References

No definition available.

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Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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- Definition

The cash outflow for the purchase of all receivables.

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The cash inflow associated with the proceeds from sale and collection of receivables during the period.

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