Investments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The table below presents disclosures about the fair value of financial assets and liabilities measured at fair value on a recurring basis in the Company's financial statements as of December 31 (in millions):

	2018								2017
	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	1,694	$	1,694	$	—	$	—	$	1,482	$	1,482	$	—	$	—
Short-term investments:
Corporate debt	1,023		—		1,023		—		958		—		958		—
Asset-backed securities	746		—		746		—		753		—		753		—
U.S. government and agency notes	108		—		108		—		113		—		113		—
Certificates of deposit placed through an account registry service ("CDARS")	75		—		75		—		120		—		120		—
Other fixed-income securities	116		—		116		—		188		—		188		—
Other investments measured at NAV	188		—		—		—		184		—		—		—
Restricted cash	105		105		—		—		109		109		—		—
Long-term investments:
Equity securities	249		249		—		—		99		99		—		—
Enhanced equipment trust certificates ("EETC")	18		—		—		18		22		—		—		22
Avianca Holdings S.A. ("AVH") Derivative Assets	11		—		—		11		—		—		—		—

Carrying Values and Estimated Fair Values of Financial Instruments

The table below presents the carrying values and estimated fair values of financial instruments not presented in the tables above as of December 31 (in millions). Carrying amounts include any related discounts, premiums, issuance costs and origination costs:

	2018										2017
	Carrying Amount		Fair Value								Carrying Amount		Fair Value
			Total		Level 1		Level 2		Level 3				Total		Level 1		Level 2		Level 3
Long-term debt	$	13,445	$	13,450	$	—	$	9,525	$	3,925	$	13,268	$	13,787	$	—	$	10,115	$	3,672
Synergy Term Loan	478		422		—		—		422		—		—		—		—		—