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Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Nov. 30, 2018	Apr. 30, 2018
Synergy
Fair Value [Line Items]
Loan amount		$ 456
Number of shares pledged as loan collateral (in shares)		516,000,000
Azul
Fair Value [Line Items]
Equity stake			2.00%
Azul | Preferred Stock
Fair Value [Line Items]
Equity stake			8.00%
Asset-Backed Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
Asset-Backed Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	16 years
Corporate Debt | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
Corporate Debt | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	3 years
CDARS | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
U.S. Government and Other Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
Other Fixed-Income Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	2 years

X

- Definition

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- Definition

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- Definition

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