TREASURY STOCK - Summary of Stock Repurchase Activities (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Repurchases (in shares)	685	4,445	3,100
Repurchases	$ 1,264	$ 8,153	$ 6,012
General authorization for shares withheld on stock award vesting (in shares)	84	87	80
General authorization for shares withheld on stock award vesting	$ 142	$ 151	$ 162
Shares repurchased in December and settled in following January (in shares)	0	19	43
Shares repurchased in December and settled in following January	$ 0	$ 40	$ 74
Authorized stock repurchase programs
Equity, Class of Treasury Stock [Line Items]
Repurchases (in shares)	601	4,358	3,020
Repurchases	$ 1,122	$ 8,002	$ 5,850