INCENTIVE PLANS - Incentive Compensation Cost (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	$ 2,021	$ 2,251	$ 2,183
Immediately Vested Stock Award
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	75	70	73
Retirement Eligible Employees | Restricted and Deferred Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	669	659	555
Nonretirement Eligible Employees | Restricted and Deferred Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	435	474	509
Deferred Cash Awards and Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	202	354	336
Variable Incentive Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Incentive compensation cost	$ 640	$ 694	$ 710
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Number of shares available for grant	42.4