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LONG-TERM DEBT - Detail on Long-term Debt Balances (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Credit Facility	$ 0		$ 0
Finance lease obligations	157
Finance lease obligations			163
Long-term debt	10,940		9,347
Less: Current portion of long-term debt	(977)		(833)
Long-term debt, noncurrent	9,963		8,514
Commercial paper
Debt Instrument [Line Items]
Commercial paper	3,197		2,245
Other
Debt Instrument [Line Items]
Other	247		223
Series K Notes, interest rate of 3.0%, face amount of $600, matured March 1, 2019 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Senior Notes	$ 0		600
Series K Notes, interest rate of 3.0%, face amount of $600, matured March 1, 2019 (effective interest rate of 4.4%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.00%
Senior notes, face amount	$ 600
Senior notes, effective interest rate	4.40%
Series L Notes, interest rate of 3.3%, face amount of $350, maturing September 15, 2022 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Senior Notes	$ 349		349
Series L Notes, interest rate of 3.3%, face amount of $350, maturing September 15, 2022 (effective interest rate of 3.4%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.30%
Senior notes, face amount	$ 350
Senior notes, effective interest rate	3.40%
Series M Notes, interest rate of 3.4%, face amount of $350, maturing October 15, 2020 (effective interest rate of 3.6%)
Debt Instrument [Line Items]
Senior Notes	$ 349		349
Series M Notes, interest rate of 3.4%, face amount of $350, maturing October 15, 2020 (effective interest rate of 3.6%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.40%
Senior notes, face amount	$ 350
Senior notes, effective interest rate	3.60%
Series N Notes, interest rate of 3.1%, face amount of $400, maturing October 15, 2021 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Senior Notes	$ 398		397
Series N Notes, interest rate of 3.1%, face amount of $400, maturing October 15, 2021 (effective interest rate of 3.4%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.10%
Senior notes, face amount	$ 400
Senior notes, effective interest rate	3.40%
Series O Notes, interest rate of 2.9%, face amount of $450, maturing March 1, 2021 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Senior Notes	$ 449		448
Series O Notes, interest rate of 2.9%, face amount of $450, maturing March 1, 2021 (effective interest rate of 3.1%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	2.90%
Senior notes, face amount	$ 450
Senior notes, effective interest rate	3.10%
Series P Notes, interest rate of 3.8%, face amount of $350, maturing October 1, 2025 (effective interest rate of 4.0%)
Debt Instrument [Line Items]
Senior Notes	$ 346		345
Series P Notes, interest rate of 3.8%, face amount of $350, maturing October 1, 2025 (effective interest rate of 4.0%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.80%
Senior notes, face amount	$ 350
Senior notes, effective interest rate	4.00%
Series Q Notes, interest rate of 2.3%, face amount of $750, maturing January 15, 2022 (effective interest rate of 2.5%)
Debt Instrument [Line Items]
Senior Notes	$ 747		745
Series Q Notes, interest rate of 2.3%, face amount of $750, maturing January 15, 2022 (effective interest rate of 2.5%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	2.30%
Senior notes, face amount	$ 750
Senior notes, effective interest rate	2.50%
Series R Notes, interest rate of 3.1%, face amount of $750, maturing June 15, 2026 (effective interest rate of 3.3%)
Debt Instrument [Line Items]
Senior Notes	$ 744		743
Series R Notes, interest rate of 3.1%, face amount of $750, maturing June 15, 2026 (effective interest rate of 3.3%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.10%
Senior notes, face amount	$ 750
Senior notes, effective interest rate	3.30%
Series T Notes, interest rate of 7.2%, face amount of $181, matured December 1, 2019 (effective interest rate of 2.3%)
Debt Instrument [Line Items]
Senior Notes	$ 0		188
Series T Notes, interest rate of 7.2%, face amount of $181, matured December 1, 2019 (effective interest rate of 2.3%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	7.20%
Senior notes, face amount	$ 181
Senior notes, effective interest rate	2.30%
Series U Notes, interest rate of 3.1%, face amount of $291, maturing February 15, 2023 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Senior Notes	$ 291		291
Series U Notes, interest rate of 3.1%, face amount of $291, maturing February 15, 2023 (effective interest rate of 3.1%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.10%
Senior notes, face amount	$ 291
Senior notes, effective interest rate	3.10%
Series V Notes, interest rate of 3.8%, face amount of $318, maturing March 15, 2025 (effective interest rate of 2.8%)
Debt Instrument [Line Items]
Senior Notes	$ 332		335
Series V Notes, interest rate of 3.8%, face amount of $318, maturing March 15, 2025 (effective interest rate of 2.8%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.80%
Senior notes, face amount	$ 318
Senior notes, effective interest rate	2.80%
Series W Notes, interest rate of 4.5%, face amount of $278, maturing October 1, 2034 (effective interest rate of 4.1%)
Debt Instrument [Line Items]
Senior Notes	$ 291		292
Series W Notes, interest rate of 4.5%, face amount of $278, maturing October 1, 2034 (effective interest rate of 4.1%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	4.50%
Senior notes, face amount	$ 278
Senior notes, effective interest rate	4.10%
Series X Notes, interest rate of 4.0%, face amount of $450, maturing April 15, 2028 (effective interest rate of 4.2%)
Debt Instrument [Line Items]
Senior Notes	$ 444		443
Series X Notes, interest rate of 4.0%, face amount of $450, maturing April 15, 2028 (effective interest rate of 4.2%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	4.00%
Senior notes, face amount	$ 450
Senior notes, effective interest rate	4.20%
Series Y Notes, floating rate, face amount of $550, maturing December 1, 2020 (effective interest rate of 2.5% at December 31, 2019)
Debt Instrument [Line Items]
Senior Notes	$ 549		547
Series Y Notes, floating rate, face amount of $550, maturing December 1, 2020 (effective interest rate of 2.5% at December 31, 2019) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, face amount	$ 550
Senior notes, effective interest rate	2.50%
Series Z Notes, interest rate of 4.2%, face amount of $350, maturing December 1, 2023 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Senior Notes	$ 347		347
Series Z Notes, interest rate of 4.2%, face amount of $350, maturing December 1, 2023 (effective interest rate of 4.4%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	4.20%
Senior notes, face amount	$ 350
Senior notes, effective interest rate	4.40%
Series AA Notes, interest rate of 4.7%, face amount of $300, maturing December 1, 2028 (effective interest rate of 4.8%)
Debt Instrument [Line Items]
Senior Notes	$ 297		297
Series AA Notes, interest rate of 4.7%, face amount of $300, maturing December 1, 2028 (effective interest rate of 4.8%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	4.70%
Senior notes, face amount	$ 300
Senior notes, effective interest rate	4.80%
Series BB Notes, floating rate, face amount of $300, maturing March 8, 2021 (effective interest rate of 2.5% at December 31, 2019)
Debt Instrument [Line Items]
Senior Notes	$ 299		0
Series BB Notes, floating rate, face amount of $300, maturing March 8, 2021 (effective interest rate of 2.5% at December 31, 2019) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, face amount	$ 300	$ 300
Senior notes, effective interest rate	2.50%
Series CC Notes, interest rate of 3.6%, face amount of $550, maturing April 15, 2024 (effective interest rate of 3.9%)
Debt Instrument [Line Items]
Senior Notes	$ 564		0
Series CC Notes, interest rate of 3.6%, face amount of $550, maturing April 15, 2024 (effective interest rate of 3.9%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	3.60%	3.60%
Senior notes, face amount	$ 550	$ 550
Senior notes, effective interest rate	3.90%
Series DD Notes, interest rate of 2.1%, face amount of $550, maturing October 3, 2022 (effective interest rate of 2.4%)
Debt Instrument [Line Items]
Senior Notes	$ 543		$ 0
Series DD Notes, interest rate of 2.1%, face amount of $550, maturing October 3, 2022 (effective interest rate of 2.4%) \| Senior Notes
Debt Instrument [Line Items]
Senior notes, interest rate	2.125%
Senior notes, face amount	$ 550
Senior notes, effective interest rate	2.40%