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FINANCING ACTIVITIES - Narrative (Details)			1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 12, 2020 USD ($)	Feb. 28, 1997 USD ($)	Oct. 31, 2016 USD ($) Mortgages	Dec. 31, 2021 USD ($) aircraft $ / shares	Dec. 31, 2021 USD ($) aircraft $ / shares	Dec. 31, 2020 USD ($) aircraft	Dec. 31, 2019 USD ($)	Nov. 23, 2020	Jul. 31, 2020 USD ($)	Jun. 08, 2020 USD ($)	May 04, 2020 USD ($)	May 01, 2020 USD ($) $ / shares	Apr. 24, 2020 USD ($)	Apr. 01, 2020 USD ($)	Mar. 30, 2020 USD ($)	Feb. 29, 2020 USD ($)	Nov. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)	Oct. 03, 2007 USD ($) Mortgages
Debt Instrument [Line Items]
Initial conversion price (in USD per share) | $ / shares				$ 38.48	$ 38.48
Loss on partial extinguishment of convertible notes					$ 28,000,000	$ 0	$ 0
Equity feature of partial extinguishment of convertible notes					(92,000,000)
Minimum level of liquidity required				$ 1,500,000,000	1,500,000,000
Outstanding letters of credit				124,000,000	124,000,000
Net book value of assets pledged as collateral for the Company's secured borrowings, primarily aircraft and engines				2,200,000,000	2,200,000,000
2022				453,000,000	453,000,000
2023				1,300,000,000	1,300,000,000
2024				81,000,000	81,000,000
2025				3,700,000,000	3,700,000,000
2026				350,000,000	350,000,000
Thereafter				5,100,000,000	5,100,000,000
364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000
Term (in years)	364 days
Revolving Credit Facility
Debt Instrument [Line Items]
Amount drawn on credit agreement	$ 1,000,000,000
Credit outstanding	0
Maximum borrowing capacity				1,500,000,000	1,500,000,000
Convertible Notes
Debt Instrument [Line Items]
Principal amount				2,097,000,000	$ 2,097,000,000	2,300,000,000
Term (in years)					5 years
Debt repurchased, face amount				203,000,000	$ 203,000,000
Cash paid to repurchase debt				$ 293,000,000	293,000,000
Reduction in debt discount and issuance costs					30,000,000
Equity feature of partial extinguishment of convertible notes					$ 92,000,000
Effective interest rate (as a percent)				5.20%	5.20%
Interest expense					$ 110,000,000
Non-cash amortization of debt discount						73,000,000
Non-cash amortization of debt issuance costs						9,000,000
Contractual coupon interest						28,000,000
If-converted value exceeded principal amount					$ 238,000,000
Secured Debt by Four Aircraft
Debt Instrument [Line Items]
Face amount of debt						125,000,000
Face amount, net of fees						$ 121,000,000
Aircrafts secured to debt transactions | aircraft						4
Secured Debt by Four Aircraft | LIBOR
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)						1.40%
Total 5.125 Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Principal amount									$ 2,000,000,000
5.125 Unsecured Notes due 2027
Debt Instrument [Line Items]
Face amount of debt										$ 1,300,000,000
Term (in years)						364 days
5.125% Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				5.125%	5.125%	5.125%
Principal amount				$ 2,000,000,000	$ 2,000,000,000	$ 2,000,000,000			700,000,000
Secured Debt by Six Aircraft
Debt Instrument [Line Items]
Face amount of debt						197,000,000
Face amount, net of fees						$ 190,000,000
Aircrafts secured to debt transactions | aircraft						6
Secured Debt by Six Aircraft | LIBOR
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)						1.40%
5.25% Notes due 2025
Debt Instrument [Line Items]
Face amount of debt						$ 1,550,000,000					$ 1,250,000,000
Term (in years)						364 days
5.25% Notes due 2025 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				5.25%	5.25%	5.25%
Principal amount				$ 1,550,000,000	$ 1,550,000,000	$ 1,550,000,000			$ 300,000,000
4.75% Notes due 2023
Debt Instrument [Line Items]
Face amount of debt						$ 1,250,000,000				$ 500,000,000	$ 750,000,000
Interest rate stated in the debt agreement (as a percent)											4.75%
Term (in years)						364 days
4.75% Notes due 2023 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				4.75%	4.75%
Principal amount				$ 1,250,000,000	$ 1,250,000,000	$ 1,250,000,000
1.25% Convertible Notes due 2025
Debt Instrument [Line Items]
Conversion ratio (in shares)				0.0259909
Initial conversion price (in USD per share) | $ / shares												$ 38.48
1.25% Convertible Notes due 2025 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				1.25%	1.25%
1.25% Convertible Notes due 2025 | Convertible Notes
Debt Instrument [Line Items]
Face amount of debt												$ 2,300,000,000
Interest rate stated in the debt agreement (as a percent)												1.25%
Principal amount				$ 1,842,000,000	$ 1,842,000,000	1,945,000,000
364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000
Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt														$ 2,300,000,000
Aircrafts secured to debt transactions | aircraft				73	73
Term (in years)	364 days
Amended 364-Day Term Loan Credit Facility | LIBOR
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)								1.00%
Amended 364-Day Term Loan Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)								1.00%
Amended 364-Day Term Loan Credit Facility | New York Fed Bank Rate
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)								0.50%
Amended 364-Day Term Loan Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)								1.00%
2.625% Notes due 2030
Debt Instrument [Line Items]
Face amount of debt																$ 500,000,000
2.625% Notes due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)																2.625%
Principal amount				$ 500,000,000	$ 500,000,000	500,000,000
2.75% Notes due 2022
Debt Instrument [Line Items]
Face amount of debt																	$ 300,000,000
Interest rate stated in the debt agreement (as a percent)																	2.75%
2.75% Notes due 2022 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				2.75%	2.75%
Principal amount				$ 300,000,000	$ 300,000,000	300,000,000
Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Face amount of debt																	$ 300,000,000
Interest rate stated in the debt agreement (as a percent)																	3.45%
Unsecured Senior Notes Due 2027 - 3.45% | Treasury Rate
Debt Instrument [Line Items]
Spread on variable rate (as a percent)		20.00%
3.00% Notes due 2026
Debt Instrument [Line Items]
Face amount of debt																		$ 300,000,000
Interest rate stated in the debt agreement (as a percent)																		3.00%
3.00% Notes due 2026 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				3.00%	3.00%
Principal amount				$ 300,000,000	$ 300,000,000	300,000,000
Term Loan Agreement Due 2026 - 3.03%
Debt Instrument [Line Items]
Number of mortgages on secured aircraft | Mortgages			7
Term Loan Agreement Due 2026 - 3.03% | Maximum
Debt Instrument [Line Items]
Face amount of debt			$ 215,000,000
Term Loan Agreement Due 2026 - 3.03% | LIBOR
Debt Instrument [Line Items]
Spread on variable rate (as a percent)			1.10%
Pass Through Certificates due 2022 - 6.24%
Debt Instrument [Line Items]
Face amount of debt																			$ 500,000,000
Number of mortgages on secured aircraft | Mortgages																			16
Pass Through Certificates due 2022 - 6.24% | Interest rate derivatives | Cash Flow Hedging
Debt Instrument [Line Items]
Notional amount																			$ 20,000,000
Pass Through Certificates Series A
Debt Instrument [Line Items]
Face amount of debt																			$ 412,000,000
Interest rate stated in the debt agreement (as a percent)																			6.15%
Pass Through Certificates Series B
Debt Instrument [Line Items]
Face amount of debt																			$ 88,000,000
Interest rate stated in the debt agreement (as a percent)																			6.65%
7.375% Debentures due 2027
Debt Instrument [Line Items]
Face amount of debt		$ 100,000,000
Interest rate stated in the debt agreement (as a percent)		7.375%
7.375% Debentures due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)				7.375%	7.375%
Principal amount				$ 116,000,000	$ 116,000,000	$ 119,000,000
Accordion Feature to Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt													$ 350,000,000
Accordion feature on short-term debt															$ 417,000,000

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